Conference vicki::boats

    Sounds like two problems.  You said you can get the same rpm for a
    different boat speed.  So have you changed the load, bottom paint
    etc.  The main problem is the poor running.  The first thing to check
    is the the compression.  This will tell you if you have any valve/ring
    problems.  If this is ok  IE all the numbers within 20% then start
    checking the ingnition.  The other thing you may see is a stretched
    timing chain/jumped timing chain.  This would cause a loss of power
    and an increase in running temp.  You did not say how many hours
    where on the engine.
    
    The other quick test would be an idle vacuum check.  A loose or
    cracked manifold would give a rough idle.  
    
    Good luck
    
    KC
    

    dave,

    	Rough idle and loss of power could be the valves. My 1987 351 PCM
    owner's manual states "Only use unleaded fuel in emergencies". Your
    engine may not appreciate unleaded, either.

    	What's the easiest way to check the valves guys? Compression test 
    would mean valves or rings, right?

    Rick

    Rough Idle sounds to me like a valve/vacuum problem, but I'm not a
    mechanic.  A vacuum gauge will give some indication as to your valves
    condition, and their ability to seat well.  Check any/all vacuum hoses
    in the intake, carb area carefully for leaks.

    350 Chevy of this time period is known for valve problems.  It seems
    that Chevy tried to save some money by making the castings a bit
    thinner.  The result is cracks in the exhaust valve seats and burned
    exhaust valves.  To check which type of heads you have, look at the
    head edge just below the spark plug holes where the head meets the
    block.  If this edge is strait you have the thicker heads, if the edge
    is "scalloped" then you have the thin heads.  This problem usually
    surfaces around 80 - 100k miles for a car.  I had it around 400 Hrs on
    my boat.  I had an '82 with 350 Mercs.  The Merc heads were
    interchangeable with automotive heads, some type of truck, I think.

    Matt

re: .1

I will check the hours, I bought the nineteen footer with 76  hours and I tend
to put on 200 hours a year, my guess is about 700 hours. But I will check.

Could be two problems, I didn't wax the bottom this year (no bottom paint)\
and the merc prob is still a virgin after four seasons, maybe the blades are
flexing more than usual compare to a new merc prop. 

The running temp is the same, I noticed a rough idle late last fall and thought
it was from bad load of gas.  It does not backfire and looking in to carb there
seems to be even amount of gas flowing from all jets.  I will do a compression
test and post results.

re: .2

My merc shop manual states NEVER use unleaded and NEVER use ethanol blend.

I will first try some lead additive.

re: .3

I will check all hoses for cracks and post which type of head I have.

Thanks for you inputs, stay tuned.

Dave 

Dave,

I had a very similar problem this year with a MUCH smaller Mercruiser (a 120)
that turned out to be fouled up needle valves. I simply turned them all the 
way in, frimly, and then backed them out to their original position (keep track
of the turns).

The engine then ran great! You might want to check the timing as well. Many 
times problems that look like fuel are actualy electrical. You might also
want to spary a LITTLE WD-40 on the inside of the distributor and cap.

Good luck!

Don
 

    Dave,
    
    As an old mech I suggest you do the following, single order, process of
    elimination:
    
    Electrical:
    
    Check all plugs for proper gap and clean.
    Check all plug wires for potential leaks (be careful you are on or near
    water I presume).
    Check distributor cap for leak, cracks and proper fit.
    Check for proper operation of vacuum advance.
    Check points for proper gap and clean (unless you have an electronic
    ignition then this shouldn't be necessary and the EI needs a special
    meter to check out).
    Check condensor for proper discharge by hold a plug wire 1 inch from a
    metal surface and cranking the engine. If the spark doesn't jump the
    gap but does at shorter distances you might want to replace the
    condensor. BE CAREFUL of FUEL and WATER else you might not finish the
    job. Don't hold the bare end of the wire either. Maybe you ought to
    forget this one and consider that the plugs are firing an indication
    that the condensor is fine (and it probably is else the engine would
    garbabge up at speed or on acceleration).
    Check all vacuum hoses for leaks and ensure proper seating and fit.
    
    Fuel:
    
    Check for contaminants in fuel, fuel lines, filters and carb float
    bowls. Contaminants include water!
    Check for proper operation of fuel pump.
    Check for proper jet setting and that jets are clean.
    Check for fuel leaks! (Perhaps before you do anything).
    Check float levels in carb.
    Take the boat out for a ride and crank it up and blow out potential
    contaminants (now that sounds like fun).
    
    Air flow:
    
    Check airfilter to ensure it is clean and free flowing, no
    contaminants.
    Check for airleaks around airfilter or airflow system.
    
    Valves:
    
    Check for proper setting if mechanical and requiring setting.
    
    If none of this works - call Zippy, he might know!
    

    Dave, two things that I didn't see mentioned before is to check for
    proper choke operation once the engine is warmed up and if you have 
    a built-in gas tank, the vent screen is not plugged up.  Does the
    engine seem to run ok when warming up?  When was your last complete
    tune-up done (set timing, adjust carb, etc.)?  It sounds to me like the
    carb could use a rebuild which depending on your ability you could do
    yourself.  I would certainly check the compression in the engine before
    I spent any money but if the engine seems to run ok before it get's
    warmed up I would suspect a carb problem.  Maybe you could borrow
    someone else's know good carb to see if the problem goes away.
    Good Luck!
    Wayne

    Dave, the last sentence should have read "known good carb", not "know
    good carb".  I already think that you may have a "no good carb".
    By the way, don't Merc 260's run Holly Marine carbs?  They are
    supposedly real simple to rebuild/replace.
    Wayne

    Merc 260's have the plain old Rochester Quatrobogs.  
    
    Test the ingnition the test the compression.  If the carb is running
    lean at WOT the first symptom maybe pinging rather than a misfire.
    Merc sets up the carb to be rich at WOT to reduce the chance of
    detonation.
    
    Ken
    

    I just realized that the question asked by Rick in .2 hasnt been
    answered so I'll take a shot at it.
    
    If a cylinder shows low compression put a spoonful of oil into the
    cylinder, crank the engine a few revs and retest.  If the compression
    goes up then the rings are probably worn.  There are more difinitive
    tests using compressed air, but for quick and dirty it can point you in
    the right direction.
    
                                              Tom

Thanks for all the replies!

I had a few minutes to spend on board last weekend and here is what I found (and
didn't find).

I have one - two inch long vacuum hose on the Rochester carb. It's used to
open the second stage butterfly.  No cracks found. Carb bolts are tight.

The carb seems to be working fine. While running the engine at all speeds and
looking down into it, there is plenty of gas evenly flowing.  The choke releases
after engine warms up and the second stage opens at higher RPMs/increased load.

The running temperature of the engine is 145 degrees. The rough idle and 
acceleration occurs about ten minutes after the engine has already been running
at 145 degress.  When accelerating  slowly, it sputters like running on just 
six or seven cylinders, occastionally running on all eight.

>   To check which type of heads you have, look at the
>   head edge just below the spark plug holes where the head meets the
>   block.  If this edge is strait you have the thicker heads, if the edge
>   is "scalloped" then you have the thin heads. 
Matt,

The spark plug hole is between two bolt holes, then there is a space, another
spark plug hole between two bolt holes and so on.  You said "just below the 
spark plug hole",  the head IS flush to the block just below the spark plug
hole.  The "space" is where the edge goes in (scalloped).  Please tell me which
head I have.  (I can draw it using DECwrite and mail it to you if necessary).

I added the proper amount of lead additive and it did not help.  As long as 
I can get the leaded gas, I will use it to save valves and valves seats.

The engine has 250 hours on it.

  
THE NEXT STEP:

The compression test/ spark plug inspection is first.

Check electrical system.  My merc has the Thunderbolt EI.(no vacuum advance)

Fuel system inspection, float bowl, jets, etc. (whow, now I committed).

stay tuned, again thanks!

Well the compression test passed - all measurements were between 130 and 145
psi.  I had my auto mechanic neighbor on board after the compression test.
I ran the boat for 20 minutes at various speeds before the engine started
showing my problem.  He inspected the block, manifold, carb and spark plug
wires, found nothing wrong.  He said the carb was very clean and while the
engine was running rough he looked into the carb a saw proper gas flow.
His guess was the electronic ignition, the Merc Thunderbolt IV, some kind of
heat sensitive problem, He also said the EI looks like an old Ford EI with a 
different wiring harness.  If only I had the contact to borrow one for an hour
to eliminate it.  I believe they are about $150.  I'm in a holding pattern until
I find one to borrow or stomach buying a spare.

Dave

    is this a sealed unit with a harness protruding, or is it mounted
    on a metal or something and you could test it.. my chrysler's 
    have EI but i was able to get a copy of the test process, and 
    check it out..
    
    JIm.

The Shop guide tells of a step-by-step method to trouble shoot an engine with
no spark.  Thus eliminating the coil, pickup in base of distributor and the EI.
I will look at the guide again for something just on the EI.

If I can make the problem appear when the boat is on the trailer, then I will
bring it to my neighbor's garage and put it on the SUN machine to see if it's
an electrical problem.  If it's not, this fall I will pull the heads off and 
look for hair-line cracks in valves/seats which expand when engine heats up.

Anymore ideas?

Dave

    Dave,
    
    Ideas! You want more ideas? I thought you were searching for answers?
    Well - here are some more ideas.
    
    It sounds from your descriptions that the roughness starts at between
    10 and 20 minutes of running, which does not sound like hairline cracks
    or blown head gaskets. You ought to get the same malfunction at the
    same temperature, which ought to take about the same time to reach it,
    give or take a minute or two.
    
    So it still sounds like fuel or electrons. However, you might want to
    "read" the plugs after running the engine in the rough stage for a few
    minutes. One plug fouled and discolored from the rest indicates a
    problem with that cylinder (gasket, valves, rings, cracks in head or
    cylinder walls). All plugs with about the same fouling points back to
    fuel and electrons.
    
    By the way. I didn't read back in the notes but when was the last time
    you changed or cleaned and gapped the plugs? Also, examine the plugs
    themselves for cracks in the porcelain insulators? These sometimes can
    cause the symptoms you are having but more often than not the plug
    misfires almost all the time.
    
    I'd also very carefully examine the entire fuel system (as best as one
    can) for areas where contaminants can collect and then be pulled into
    the line or for cracked (hairline) lines (but then you usually smell a
    light gasoline odor) or lines that collapse.
    
    Heat failure on EIs does happen but usually the damn (can I say that
    here?) thing goes nuts (or you do) by cutting in and out and acting  
    erratic. The SUN should show this as well as any other electron
    failure.
    
    Good luck.
    
    Old number 88
    

    Try checking your plug wires with an inductive pickup on a tach.
    Rotate the pickup around all the wires and make sure you have a
    constant rpm on all cylinders.  Assuming the rest of the ignition is 
    working, this should show an intermittent plug or wire.  This worked 
    on my Bronco when it lost power.
    
    Howard ( normally read only) 

re:.15

I changed the plugs and re-gapped.  The problem does occur about the same time
(20 min,  my first mention of 10 min was incorrect).  I will be pulling the boat
out soon, and will try get the problem to occur on the trailer.

re:-1

I understand what you are saying, but I don't know where inductive pickup is 
for the tach?

     I had a similar problem , not on a 260, but on one of my 502's..When
    things would get just warmed up one engine would exhibit just the 
    problems you have mentioned. I tried everything and finally found the
    problem, It was actually with the tack..Apparently after the tack was
    running for a while it was starting to short out which in turn caused
    a shorting out at the coil, (tack lead) never a hard short but enough 
    to cause fits.

    I had a similar problem on a merc and my mechanic was baffled. After
    hours of work, he gave up.
    
    I found the solution by accident, in desperation trying everything.
    Compression was fine, domain was fine, EVERYTHING CHECKED OUT FINE!!!
    
    The problem?
    
    I replaced the points in the distributor. INSTANT GOODNESS! My mechanic
    didn't find the problem because his domain meter said that the points
    were fine. Not so, because although they were not badly pitted and
    looked good visually, in fact they were unevenly worn and causing bad
    spark problems.
    
    Poke around, if your system has points, and see if it helps.
    
    Ray	

    The inductive pickup I am refering to is on an engine analyzer or good
    automotive type of diagnostic equipment not the boat's tach.  This would
    be used to accurately check the engines rpm. 
    
    Howard

    Moved by moderator...
    
================================================================================
Note 869.0  Poor running, then total running failure after tune up an  2 replies
JLGVS::GUNNERSON "You got what you wanted and lost " 31 lines   8-JUL-1991 12:12
--------------------------------------------------------------------------------
This year I decided to buy Peace of Mind. I.e., I have paid a boat yard to 
winterize, lube the outdrive universal, and then tune-up and make ready for
water my boat.

They've had the boat for a while and when it was first returned it was returned
with a broken water hose. This was corrected.

I get the boat back on 7/4. I add new navigational lights, install a compass,
and generally tidy things up. This work combined with the weather and other work
I had to do kept me from launching the boat before late afternoon on Saturday.
On the way to ramp I fill up with Mobil Super Unleaded.

I head out of the harbor. I am gone for only a minute or so when I notice a 
stumble, a hesitation. Then it happens again. I stop, check for possible exter-
nal factors, finding none I turn around. On the way back the engine starts 
running rougher and rougher. It back fires, it dies. I restart it anf go a 
little further in the engine running on on the ragged edge all the time. Between
restarts and paddling and the inward-bound tide we make it back with boats 
passing us all the while. We were finally towed in the last � mile. I hauled it
out and returned it to the boatyard hoping that it was something that they were
responsible for as a result of the work they did. I.e., it wouldn't cost me any-
thing. Other possibilities that I can imagine are bad new gas, contamination of
the gas that was in the tank.

The boat started and seemed to run fine while idling around the harbor, and 
heading out. It seemed to run fine for about a minute after reaching planing
speed. There is a gap in the points, the coil is producing spark, there is fuel
reaching the carb (liquid that smells like gas is being forced into the carb 
when the throttle moves forward). Any ideas?

john

    Moved by moderator...
    
================================================================================
Note 869.1  Poor running, then total running failure after tune up and f  1 of 2
ULTRA::BURGESS "Mad Man across the water"            42 lines   8-JUL-1991 12:32
                     -< A coupla ideas - I recommend DIY. >-
--------------------------------------------------------------------------------
re <<< Note 869.0 by JLGVS::GUNNERSON "You got what you wanted and lost what you had" >>>
>     -< Poor running, then total running failure after tune up and first >-

> On the way to ramp I fill up with Mobil Super Unleaded.

	Does this mean that it was winterized and stored with an empty 
or very low tank ?   If so then condensation in the fuel is a 
possibility;  though if you have a water separater, and  IF  that was 
drained off before storage....

> I head out of the harbor. I am gone for only a minute or so when I notice a 
> stumble, a hesitation. Then it happens again. I stop, check for possible exter-
> nal factors, finding none I turn around. On the way back the engine starts 
> running rougher and rougher. It back fires, it dies. I restart it anf go a 
> little further in the engine running on on the ragged edge all the time. Between
> restarts and paddling and the inward-bound tide we make it back with boats 
> passing us all the while. We were finally towed in the last � mile. I hauled it
> out and returned it to the boatyard hoping that it was something that they were
> responsible for as a result of the work they did. I.e., it wouldn't cost me any-
> thing. Other possibilities that I can imagine are bad new gas, contamination of
> the gas that was in the tank.

	Without knowing your boat and how far you got its tough to say 
whether you ran OK on what was left in the carb bowl from last year 
and then stumbled with the new gas, or what.  Its possible that it 
went bad once the sediment (tank and/or carb bowl) got stirred up.

> The boat started and seemed to run fine while idling around the harbor, and 
> heading out. It seemed to run fine for about a minute after reaching planing
> speed. There is a gap in the points, the coil is producing spark, there is fuel
> reaching the carb (liquid that smells like gas is being forced into the carb 
> when the throttle moves forward). Any ideas?


	How warmed up does this represent ?   Maybe the choke 
(probably electric)  isn't coming off.

> john


	Reg

One more time on reply...

Re. "Does this mean that it was winterized and stored with an empty 
or very low tank ?   If so then condensation in the fuel is a 
possibility;  though if you have a water separater, and  IF  that was 
drained off before storage...."

Well the tank was � full (65 - 70 gallon tank required 35 gallons to fill).

Condensation is a real possibility. Now I wish I dumped the fuel additive for
starting in spring in it. For some reason I was afraid too. Chemical soup maybe?

There is a Mercruiser (Quicksilver) water serperating filter on it. Oil filter
style. I don't think it can be drained, I was too stupid to change it.

Re. "Without knowing your boat and how far you got its tough to say 
whether you ran OK on what was left in the carb bowl from last year 
and then stumbled with the new gas, or what.  Its possible that it 
went bad once the sediment (tank and/or carb bowl) got stirred up."

Entirely possible. I drove it around the cove for about 15 minutes, and another
10 at least out of the harbor. I believe that the engine was well warmed up and
any fuel in the carb was used up before any problems appeared. The rougher 
water may have caused sediments to be picked up, but I got a strong stream of
fuel into the barrels, so I don't believe it to be simply blocked.

Like I said I can only hope (from a financial - out of my pocket cost point of
view) that it is something they did. I probably neglected something that is 
going to cost me more money.

john

I got a diagnosis from the boatyard. Worn distributor gear. Thus timing was 
being thrown off, thus the problem I experienced. Their concern is that they
have not observed this type of wear on Mercruiser engines before, maybe some-
thing is worn in the parts that drive that gear. In any case they are ordering
and replacing the worn parts. My guess is that if someone had experienced any-
thing similiar with this block they would have responded to my original note,
but in case this new information jogs any memory cells I'd be interested in any
previous experience with the same problem.

FWIW: Mercruiser 888, Ford 302 188 Hp engine.

john

John,
Stock Ford 302 engines are not "known" for having bad distributor 
drives.  In a marine application there's a good chance the camshaft 
and/or distributor are aftermarket parts, in which case anything
can happen.

Something you should consider is what happens to all of the worn
and broken off pieces of the drive gears.  I had a distributor drive
gear destroy itself in a Thunderbird Turbo 2.3 liter 4 cylinder motor.
It ground itself up, with metal filings everywhere.  The distributor 
was replaced under warranty, but when I got the car back it still had 
the same dirty oil filter on it.  They hadn't even bothered to change 
the oil.  I sold the car shortly afterward.

Some Ford motors have problems with oil pump pickups.  When the screen 
clogs with sludge or debris, a bypass valve opens up, allowing large
pieces to pass through the pump, sometimes destroying the pump in the
process.  I'm not trying to alarm you, but your worn drive gear can lead
to serious problems, especially when you can't walk home.

Rick

    You might want to have them look for something that might cause such a
    problem.. a tight/shot dirtributor shaft bearing, or (if the oil pump
    drives off the distributor) a tight oil pump.
    
    ...tom

    In the case of the distributor, i went thru this last year. Myself and
    a friend went bonkers trying to figure out what the hell it was.
    
    Popping thru the carb was a major symptom. we looked and screwed with
    everything.
    
    I gave up and turned it over to the marina. They went crazy as well.One 
    Friday, i got down there early, asked them how they had made out,
    they hadn't, sooooo i said to one of the mechanics, "get your tools"
    i'll meet you down there. He went thru a whole adjustment process,
    still no luck, (note this is electronic ignition) READ no point or 
    condensor, but the distributor pickup can be adjusted, and he did 
    that, he went back to check it, and it had changed, thats when he
    found the worn bearings, it could be moved .002" or so.
    
    After a new distributor, all was fine. 
    
    I've since ordered a rebuild kit, and rebuilt the old one.
    
    I never experienced the stalling, or not running, but at idle
    you could hear and uneveness in the exhaust at about 1k rpm.
    
    By the way, it took about 5 weeks to find the cause of the
    problem, and of course the timing was changing as the distributor
    rotated..
    
    JIm.

Sounds like it. And the timing was changing as a result of the worn gear. The 
yard's big question (and therefore mine, since the answer will cost me $$$$) is
what caused the "unusual" wear in the first place. I just called the yard. They
say that the distributor shaft spins freely as does the press-fit bearing in
the block (they thought of these, I guess, since they had the answer without 
checking.)  They tell me the bevel gear is worn so that the face of the gear is
narrower ("razor thin") at one end then the other. I'll be seeing it Saturday so
maybe I'll have more.

john

RE: .30
>>  -< Who said I should be happy to have a Ford engine? >-

Not to nit pick or anything, but the last I heard Chevy's aren't immune
from this either.  It's not a common problem, but it's no more prevalent
in a Ford than a Chevy.  

Matter of fact, Chevies have their own set of distributor problems with 
it mounted in the rear.  Camshaft flex (the dist. is at the far end, away 
from the "driven" end of the cam) causes slight timing changes.  Also, 
in some applications the dist. is a b*tch to get to at the rear of the 
motor. Some racers go as far as converting Chevies to front distributors
to avoid the slight timing changes.

One other thing I haven't heard any mention of is what you or the marina 
plan to do about the debris in the motor from the damaged gears. If you
plan to keep the boat it's not something that should be ignored.  What
happened in the motor is about the equivalent of dumping a small handful
of metal particles from a lathe or drill press into the crankcase, and 
you'd probably worry if that happened.  At minimum I'd change the oil 
and filter now, again after an hour or two running, and again after 5 or 
10 hours.

Just my $.02
Rick

Changing the oil. Well yes, I figured that went without saying. If this wear
occured in the approximately 45 minutes I had it running then all the metal
particles will be in the engine now. If it has been wearing for a while then
there should be only a trace of these particles since I just changed the oil.

jlg

    I'd be concerned about proving this, than speculating it.
    
    I go along with Rick's suggestion, but i would put a magnet in
    the oil, or strain it thru a sieve (sp) and check it for stray
    metal fragments. My guess is that its been on its way out for
    awhile and that its not a catastrophic failure.
    
    Or you could drain the oil, and send off a sample to one
    of the analysis labs, they shouldbe able to determine
    just how bad this is.
    
    JIm.

        I'm experiencing a similar problem that seems to fit with this
    discussion...

        I've got a 1980 Mastercraft with a 351 Ford PleasureCraft Marine
    Engine (approx. 800 hours).  The problem began this year.  We did
    nothing other than the usual overhaul/tune up at the beginning of the
    season (complete change of oil, plugs, filters, points, condenser,
    rotor, distributor cap...).

        We've been doing some barefooting so we've been pushing the speed
    up to 38-40 instead of the usual 32-34 for skiing.  The problem
    occurs at the higher speeds.  Once we hit 36 mph, the engine runs rough, 
    occasionally missing.  Up until that speed, everything runs fine (idle,
    acceleration, etc.).  Top-end is now 40 as opposed to the usual 44.

        The first thought that came to mind was the timing.  We got a
    timing light and checked it out.  Turned out that we were set at
    20 degrees BTDC.  The specs call for 6 degrees BTDC.  A quick turn of
    the distributor and we were all set.  We also checked the advance and
    everything looked fine (a small change in timing at higher RPMs but
    nothing drastic, maybe 2 or 3 degrees).  The engine ran great.

        However, once we put it in drive and began to move, we were
    worse off than before.  The engine coughed, missed, sputtered...
    It was apparent that we had made things much worse instead of better.
    We rechecked the timing and it hadn't moved.  We reset it to the original
    20 degrees BTDC and improved the situation, but we were no better off
    than we were at the start of the exercise.

        I'm confused.  How can the engine run better with the timing set so
    far off?  Can the timing chain jump or slip?  Can the centrifugal advance 
    need repair?  Why does the engine run so well in neutral, but run so
    poorly once the boat is in gear?

        Any assistance would be greatly appreciated.




-Dean
        

Re. .33.

I am in agreement, the "send oil to lab" is a good idea.

All I was trying to say in response to .31 in .32 was that.

1. The oil was just changed prior to discovering the worn distributor shaft gear

2. Changing the oil now is a good idea, but if that gear has been wearing out
   all along changing the oil right now probably won't be removing the amount of
   "debris" suspected of being in there.
    
The oil change just done would have been no more, or no less effective at 
getting what ever is in there out of there, than an oil change done right now.
The difference between the last oil change and doing it right now is the amount
of metal that wore off during the minutes I operated the boat last Saturday. It
is going to get done. I am just guessing that there won't be much in there any-
more since it was so recently changed.

john

    re  .34,  the problem i described a few notes was similar to what your
    seeing  ___repeat similar---
    
    at idle is was barely noticable, except you could barely hear it
    in the ehaust. for me 2800 rpm was the magic spot, you could 
    really notice the difference, popping in the carb was the major
    symptom.  and the timing was supposed to be 2 btdc, would not
    barely run at this setting.  Even now they like 10 btdc.
    
    
    I think there are 2 things affecting your timing, 800 hours
    to a small degree, and the garbage they call gasoline today.
    
    One thing iwould do is check your distributor shaft for any play,
    .002-.003 means rebuild or replace, actually there shouldn't be any
    play at all.
    
    One other thing you could do, watch your timing as you rev. the engine
    it should return to its setting every time. Another indicator..
    
    JIm.

	I had a similar problem with my SeaRay this year.  It started 
to run badly when opened up, my biggest fear was that the head gasket 
was starting to let go, so I started to do a compression test - all the 
plugs were burned out  - HUGE GAPS, the electrodes were just burned 
away, so I did the compression test anyway and replaced the plugs.  
There was still a problem, so I re-timed it and it was way off - 
hmmmm, weird, so maybe the points were a bit off ??, I re-set them 
and re-timed it again, then everything was fine for about another 10 
hours of running.  Then, when I was skiing, the engine just died.  I
climbed into the boat, my son protested that he hadn't shut it down or
tried to re-start it, it had just quit.  I cranked it a couple of
times, did the usual tricks with plug and coil leads to find there
were no sparks.  I took the cap off and found the rotor didn't even turn
when the motor was cranked.  We got towed in, I pulled the distributor 
and found 2 1/2 teeth missing from the driven gear, the rest of the 
teeth were very thin and sharp.  The next day I looked down the hole
and was able to see that the driving gear on the camshaft was in very
good shape, I also retrieved enough pieces to believe I got them all
by using a small button magnet wedged into a length of plastic tube
that I shoved down the hole.  The replacement gear cost me  $18.90  
from a store that I have sworn I shall now avoid forever, it took ~1/2 
hour to install, but retiming the engine from scratch was a pain - it 
is  NECESSARY  to get the gear teeth exactly right, you can't just 
turn the distributor around to make up for being off by one tooth, 
because the rotor won't be pointing at a plug wire if you do (-:
I ran it in the test tank for long enough to warm it up and get the 
timing exactly right, then I changed the oil  - -  well, just to be 
safe, though I suspect the filtre would stop any large bits from going 
anywhere.  Parts counter folks tell me that driving gears on camshafts
are typically a lot stronger (less likely to break) and harder (wear
less) than driven gears on distributors, sometimes the distributor
gear is fibre, nylon or plastic to save the tear down that would be
necessary to replace the camshaft.  FWIW, etc.

re Dean & the m/c

	It sounds as if your timing might be stuck advanced.... ??

	I would pull the distributor and check the centrifugal 
weights and springs for free movement (and/or attachment).

	In fact I will, if I get to your boat before you get to do it 
(-:

	Reg

Dean,
Your problem could be caused by any one of a hundred different things.  It
could be as simple as a defective spark plug, or a symptom of an engine that
is just plain tired after 800 hours.

Since it was recently worked on, I'd start by double checking everything that
was done.  It is possible for brand new points, plugs, condensers, etc. to
be defective.  Make sure the plug wires are all on right, in the correct firing
order.  Ford 351's have a different firing order than 302's, could be they
were put back with the 302 firing order, although this is unlikely since the
engine would probably barely run at all.  It could be a bad plug wire, whether
they're new or old doesn't matter.  Check the point gap with a dwell meter 
also, a slighty worn distributor cam will cause timing to be off if set by gap
(I know, we've debated this before!).

If everything appears OK, do a compression test.  If you've got a burned valve,
broken ring, or just plain tired motor no tuneup is gonna help.  Compression
should be around 150 lbs, and all within 10%. 

The problem could also be in the advance curve in your distributor. You men-
tioned you only saw a 2 or 3 degree change at higher speed.  Most motors like
about 34-36 TOTAL (initial + vacuum + mechanical) advance, which should be all
in by 2500-2800 rpm.  With an initial advance of 20 degrees, there should be 
about 16 degrees in the distrbutor, meaning the distributor should advance the 
timing 16 more degrees as it revs up.  Six degrees initial should require 30
degrees in the distrbutor.  Most marine engines have no vacuum advance, only
mechanical, which may be why the timing was set to 20 degrees initial.  By
backing it off to 6, you could be running at least 14 degrees retarded.  If
you're really only seeing 2 or 3 degrees in the distributor I would suspect 
a problem there.

Another problem could be the carb - I assume you've got a vacuum advance Holley.
If the secondary throttle plate sticks shut, top end performance will go right
to hell.  It could have rusted in place over the winter, the throttle plate 
stop could be out of adjustment causing the plate too close too far and bind.
Or a single backfire can slam the plate stuck shut, and the vacuum alone cannot
pull it open.  Also, leaky power valves can cause problems, but will also 
usually cause a rich idle and black smoke as a symptom.

As you can see, it could be a bunch of different things.  If you don't have
access to someone who really knows what they're doing, this could be one of
the times when it's cheaper in the long run to have it professionally checked
on an analyzer, rather than throwing parts at it til you happen to hit on the
right one.

Rick

Re. .37, Reg, I've forgotten (I'm sorry) what Sea Ray are you speaking of. I 
know it isn't as old as mine or powered with the same engine, but I am still
curious. (BTW folks, I realize this isn't a boat builder problem, but one of
the power supplier, and even then probably not a defect, but plain old wear
and tear as Reg states.) I am assuming you've been running fine once you got
it all straightened out?

john

re <<< Note 844.39 by JLGVS::GUNNERSON "You got what you wanted and lost what you had" >>>
>                    -< Nothing like a support group   :-) >-

> Re. .37, Reg, I've forgotten (I'm sorry) what Sea Ray are you speaking of. I 

	Sorry, I forgot to mention;

	1987 140 HP  Mercruiser I/O  4 cylinder  {GM block, I think}
	That boat has no hour meter....  I'm sure I didn't put hours 
on it at the same rate as the Nautique is clocking 'em up;  it just 
didn't seem to attract skiers the same (-:, (-:

	Anyway, the problem sounds similar to what your mechanic 
described, also parts counter talk seems to indicate that distributor 
driven gears *DO* wear down  - -  proper routine maintenance and 
regular oil changes not withstanding.  I think I'll be pulling the 
distributor off the Nautique annually from here on.

	Reg

    Reg, the plan you mention, "pulling the dist annually" was this to 
    check for wear. Catch it befor it becomes a problem??
    
    Jim????

re                     <<< Note 844.41 by HYEND::J_BORZUMATO >>>
>                              -< annual check??? >-

>    Reg, the plan you mention, "pulling the dist annually" was this to 
>    check for wear. Catch it befor it becomes a problem??

	Yes, I was planning to add it to my check list.  In going 
through this experience I picked up some misc leaflets and (re)read the 
PCM manual that came with the Nautique.  It seems a good idea to pull 
the distributor even for a points change;  just so much easier to get 
it on the bench under good light, etc.  Easy enough once you scribe 
marks on the distrib base and the block.

	Reg

    I think this problem is being a little bit exaggerated here. 
    
    
    We all know that these engines have automotive-type distributors, and
    how they are driven is off of the camshaft. The same as our cars,
    trucks, etc. (barring the trend to overhead cam engines, and
    klattermotors) so what's different about our marine engines, and their
    tendency to "wear" distributor gears? Don't [most of us] put lots more
    hours on our automobiles? I'd think that the ratio would easily be
    close to 80X more use on my car than my boat, but everybodies milage
    does vary... Why don't our cars end up in the shop for worn distributor
    gears? (Nevermind mentioning Mopars and their plastic gears--we're just
    talking cast iron/hardened steel here)
    
    The one beaming difference I can point out is that the oil in our boats
    tends to be a straight 30 or 20 weight oil, and with that comes reduced
    cold startup protection. I still fail to see anything in that point at
    all that would accelerate distributor gear wear--we're not talking
    about a high pressure load on that gear, as would be found in a gearbox
    or a transaxle. I don't think that constant RPMs would have much
    bearing in this either. 
    
    In short, I don't believe there's anything to worry about. As far as I
    can tell at this pont, JLG's worn gear has still yet to be described to
    the conference in detail of its appearance, and what's "worn" about it.
    Horror stories about missing teeth are credible, I'm sure, but they
    would have to be caused by either of A-Dremel Moto Tool-speed rotation
    or B-being dropped or forced into the hole instead of being "meshed"
    all the way in. I managed to chip 2 or 3 teeth in my Ford's gear once,
    while attempting to pull it off the shaft to replace the reluctor
    inside, and found that there was no gear availablity. New distributor
    time! I was hoping for a nice slide off the shaft once I had driven the
    drive pin out, but met up with a stuck gear to the shaft. I then
    proceeded to place the distributor in my vice, and placed a open-end
    wrench against the gear, and tried to drive it off with a hammer.
    That's how my teeth got chipped. A $100 lesson learned. Use the puller
    that's sitting 3 feet away next time!
    
    I know it's better to be safe than sorry, but pulling a distributor
    needlessly could cause more problems that it could prevent--almost a
    guaranty considering the true failure rate of the gear.
    
    And Reg, if you check your gear at winterizing time, you would be
    cutting into your Christmas shopping time! ;^)
    
    Mike

    Folks,
    
     Regarding the 351 inboard, the carb secondaries come in around that 
    speed. If they haven't been used in a while they may be clogged.
    Another thought is plain old bottom slime ( no insults intended ).
    I have seen a ski boat to speed slowed down 7 mph by slime on the
    bottom.
    
     I agree with the general ignition evaluation also. Motors with points
    take some maintenance. 
    
     Chuck

Re. 43, what you said about cars not wearing distributor gears with lots more 
use, which is why the question of why is mine so badly worn. 

Well to describe it (after direct view on a bench) was pretty much as described
to me over the phone. Since it is a three dimensional, bevel shaped with curved
gears it is difficult for me to describe or draw here. Basically each tooth on 
the gear (none missing) lookes like someone machined a nice trough into the face
with it go in deeper at one end than the other.

      __                   __    
     / /                  / /
    / /  - Normal         //  - what I got
   / /                   //
  /_/                    /


john

RE: the last few...

There may not be any answer for why your's wore out John, it could be just 
"one of those things".  Why is one car/boat/computer a gem, while an identical
one is a lemon?  Who knows?    8^)

One possibility is that from your previous notes, I know you've only owned
the boat a few years.  Could be the previous owner abused it, continually
over-revved it, neglected oil changes, used cheap oil, etc...

Another possibility that I mentioned several replies back, is that a lot
of "marinized" motors have aftermarket cams and distributors.  If one or 
both of these are aftermarket, even a slight variation from the factory 
spec could accelerate gear wear.

And yet *another* possibility if your motor has a camshaft thrust bearing.
A worn, wrong size, or missing bearing would place the cam in the incorrect
position in relation to the distributor drive gear.  This would wear out the 
distributor gear in no time at all.  I don't know offhand whether a Ford 302
has a thrust bearing or not.  

I would also have to agree that pulling the distributor for an annual check
is probably excessive.  Just as *most* cars never have a problem with these
parts, neither do boat motors.  It's likely that frequent removal of the
distributor will cause more problems than it prevents.  J'ever hear the
sickening clunk of the oil pump drive rod as it falls out of the distributor
and into the oil pan?  I did it once, and had to drop the oil pan of a freshly
rebuilt engine to retrieve it.  In a boat it would require removal of the 
engine.  A more effective annual service might be to send an oil sample to 
that company that does mail order oil analysis.  They can tell you if your 
distributor drive or any other parts are on their way out to lunch.

Rick

> Re. 43, what you said about cars not wearing distributor gears with lots more 
> use, which is why the question of why is mine so badly worn. 

	Only a couple of things I can think of;

i)	Our cars probably don't sit as long and drain their oil into 
the sump as often or as completely.  Lube to the distributor gear 
appears to be via whatever oil is on its way back down.
area.

ii)	They're  NOT  auto distributors, typically they're from 
smaller companies.....  there's at least a chance that they're less 
reliable as a result.

iii)	As I said in a previous reply, this gear is "failsafe" by 
design to save the camshaft gear - even in autos.  Whether this is 
moreso for marine applications  ?? go ahead and speculate.

>
>       __                   __    
>      / /                  / /
>     / /  - Normal         //  - what I got
>    / /                   //
>   /_/                    /


	Yep;  and when mine got thin enough a couple of 'em broke, at 
some point the camshaft gear skipped and cut out its profile on maybe 
3 others.

	Reg

Re. .46, you know, if it was "just one of those things", or even if it wore out
due to abuse/neglect by either the previous owner or myself I wouldn't feel too
badly about it. What I mean is it is a simple, and relatively speaking situation
whereby;

 A. Engine won't run 
 B. Worn distributor gear found
 C. Gear replaced
 D. Apply liberal sums of money to boat yard
 C. Drive boat happily ever after (or at least to next problem :-)

You know a "simple" problem that is fixed and you are on your way. What I fear,
and the reason for the query, is that the gear is only the tip of an iceberg of
problems (i.e., that the gear isn't *the* problem, only a symptom of larger
problems) and repair expenses. I guess time will tell, beacuse the cam gear 
looks fine and I am not going to tear down the engine now to determine if it is
something else. I figure that if something starts wearing this gear accelerated
mean time to timing adjustments to keep it running right will be the first sign
of a larger problem. If it looks like it is happening, then I would consider
pulling the distributor to visually check it out, since there is a history, and
a possibility of a known problem. However, I agree that pulling the distributor
(and the possibiities for screwing things up) as regular PM probably isn't 
something I would do.

Re. last couple. In regards to the distributor, I am certain it is a Mercruiser
part (where they got it I don't know), as when I did tune-ups I had to ascertain
what type of distributor my particular 888 had before proceeding in the repair
manual to the next step.

    Good story, John.
    
    The drawing of your gear is indicating to me that the gear is not
    wearing (meshing) against its entire length, but rather, it's wearing
    on half of its length. It would seem like a seating (depth) problem,
    whereby the cam and distributor gear appear to have just too much
    distance between them. I'll check my old ford distributor and its wear
    pattern tonight. Glad to hear the boat lives! In this weather, it's
    needed!
    
    Reg, you've made a series of good points, especially in pointing out
    how a gear can get worn and then go a step further and actually wear
    away! 
    
    Now let's go jump in/on a lake and cool off!
    
    Mike

Re. .49, well it doesn't live yet. The new gear has arrived, but as if 10:30 AM
it wasn't installed yet. Also, like I said the drawing was crude, the gear was
worn for its entire length, but it wasn't equally worn. The wear pattern was 
continuous, with the wear being much heavier at one end of the tooth than the
other. Sort of the process you'd use if you had to make a wedge out of a block
and you didn't have a saw (or a way to split it).

john

    
    
    If the distributor drive gear was that badly worn, what does the worm
    gear on the cam look like? If that is chewed up , that new gear may be 
    engine eating filings in a copuple of hours.
    
     Usually when a gear is that bady worn, it,s mating gear is histiry,
    also, and in this case, that means time to replace the camshaft as the
    worm gear is part of the cam.

    
    
    It sounds as if the gear "preload" might be wrong.  Preload is the
    actual spacing between the gear teeth while they are meshed, and is
    responsible for proper wear between gears.  I don't know if it can 
    be adjusted in this case, but the engine rebuild manual would have 
    that information.  If it is adjustable, then anyone installing an
    aftermarket distributor(marine engine builder or others) had better
    get the adjustment perfect, or excess wear will occur rather quickly.
    If the pre load is too great, i.e. too much space between the tooth
    surfaces, then the gears will tend to thin out on the edges.  If the
    gear preload is too small,  i.e. too little space, the gears will tend
    to bind and wear grooves in the face of the teeth.  Again, I don't
    know if there is an adjustment for distributor gear preload, but it
    is definitely worth an investigation, as we already know that the
    distributors have been installed outside of the manufacturers control.
    As someone has already mentioned, verticle alignment of the gears is
    also critical, and is indicated by the wear patterns on the gear teeth.
    
    As far as initial timing adjustment goes, someone mentioned that most 
    marine distributors do not use vacuum advance.  If your distributor
    does employ a vacuum advance mechanism, it is IMPERATIVE that you
    remove the vacuum line from the distributor and plug it BEFORE you
    check the timing with a light.  Initial timing figures are given for
    exactly that, initial timing, before any kind of automatic advance
    takes place.  Initial timing is best set WITHOUT the use of a Timing
    light.  If you have ignition points, you can use a continuity tester
    in series with the primary ignition circuit(points).  Disconnect the 
    thin wire running from the coil to the distributor(points).  Insert
    a continuity tester(12v bulb will do) in series, between the battery
    and the distributor(points) using this wire.  Set the engine flywheel
    timing marks for 6 degrees or whatever your spec happens to be, by
    turning the engine over by hand or "bumping" it with the starter. 
    Be sure to get the timing marks "right on" or as close as possible
    for the most accuracy.  Also be sure that number 1 piston is
    approaching Top Dead Center(TDC) on the compression stroke.  You can
    do this by removing the #1 plug and holding your thumb or heel of
    your hand over the plug hole in the head.  When the piston is rising
    on the compression stroke, the pressure build up in the cylinder will
    try to push your hand away.  If you have #1 approaching TDC and the
    timing marks indicate that it is 6 degrees(or your spec) away from TDC,
    then connect the continuity tester(or bulb) from the battery to the
    ignition points(which are basically a switch to ground) and rotate the
    distributor housing slightly until the light just goes out.  Make sure 
    that the rotor is pointing towards the #1 plug wire tower on the
    distributor cap(especialy if you have had the distributor out of the 
    engine).  When the light just goes out, it indicates that the points 
    have just opened the primary circuit causing the electro-magnetic field
     around the coil to collapse, inducing current to flow in the secondary
    (spark plug) ignition circuit.  This secondary circuit is the stepped up
     side of the coil(transformer) and produces the high voltage needed to 
    "fire" a spark plug by jumping its gap.  Of course, with the primary wire 
    disconnected from the points and a continuity tester installed, the 
    ignition circuits are inoperative.  The above scenario is what actually
     happens during operation(as much as thousands of times per second!).  
    This is the best way to set "static" or "initial" ignition timing, and 
    the only proper way to set an aircraft or race engine's ignition timing.
    It is far and away the most accurate method.  However, as you can see by 
    my description, it is not the most convenient.  Thus the invention of the
    neon timing light.  If using a timing light that triggers from the 
    secondary ignition circuit(spark plug wire), always remember to disable 
    the vacuum advance mechanism(if applicable) as a false reading will most 
    likely occur if you do not!  Unlike mechanical advance which takes effect 
    at a slightly higher RPM, vacuum advance is operational at the high end of
    idle(under 10000 RPM in most cases) and will cause you to see more advance
    than is statically set.  This could easily account for a reading as high 
    as 20 degrees with as little as 6 degrees of static ignition advance.
    
    Don

    re: .52
    
    I know its a typo but "high end of idle (under 10000 RPM)" WHEW! That
    sucker must have one heck of a cam overlap and rev beyond belief.
    
    Acutally, Don's suggestion is good but somewhat excessive for the
    average engine. If properly used, a good timing light will get
    accurate results +/- 1 degree or so. But, if your are a stickler
    for perfection then you need to tear the engine down to the short
    block and time the cam and the ignition all at once, at an even higher
    degree of mechanical accuracy than Don's outside the block method. But,
    it doesn't sound like this baby is going to run indy - so use a good
    timing light according to the directions. And don't grab the plug
    wire unless you get your jollies that way!

re; .1-.20

Well, its fixed and I'm very red in the face.  It's hard to write this reply
after I sent myself done the garden path, but I owe it to all noters that
participated.

I seems that the new (last year) $23 merc distributor cap may have had a flaw.
The center contact (button) was completely gone.  I don't understand how the 
engine could run fine for the first 20 minutes and then start acting up.  But
that shall remain a mystery.

Last year before our family trip up the Mississippi to the twin cities, I 
throughly went over the boat replacing things that were slightly worn such as
belts, hoses, plugs, DISTRIBUTOR CAP and ROTOR.  I then keep the slightly worn
parts on-board as emergency spares along with spare prop, prop nuts, 
washer, etc.

I didn't want to have any problems since this was our first big adventure with 
our two very young kids.  The trip was great with no problems, little did I know
my problems were yet to come!

Because I replaced the dist. cap/rotor and plugs JUST last year, the problem 
couldn't be with cap.  This kind of thinking sent me down the garden path even 
after fellow boaters suggested a few times to check the electrical system.

There must have been a gap between the center button on the cap and spring 
lever (contact) on the rotor right from the start.  The constant arcing  
ate away the buttom.  Three of the four bolts holding the cap in place were 
fused to the dist. base.  I had to snap the bolts to get the old cap off, then
pull the distributor to re-tap the holes.  What a chore!

Well the 260 is running as well as it will ever.

Thanks to all that participted.

Dave

I got my boat back. With the distributor gear as a souvenier. Launched it Sat-
urday in the pouring rain, and ran it yesterday with no problems. After a more
through testing of everything the yard also replaced the ignition wires an coil
for smoother running at higher RPMs. Only wish I could place a photograph in the
conference so anyone who is curious could see it. Hope the new one lasts a while
for me. The drive gear on the cam looks fine.

Now to find a place to send an oil sample. Course I could probably just send 
money. That seems to be really want anyone wants anyway :-)

john

    On a place to send an oil sample:
    
    If my memory serves me right, the Boat U.S. catalog has one in it.
    I think its about $17.95 ?? but anyway it includes the analysis.
    
    If the claim they make about what info they can provide, its worth
    it,
    
    Let us know, maybe we're all missing something..
    
    JIm

re oil testing:

Unless something is grossly wrong with your engine, a single oil 
analysis won't tell you much. The analysis tells you how many parts per 
million of various things (iron, silicon, lead, aluminum, etc) are in 
your oil and the percentage of water and fuel dilution. Every engine is 
a different combination of metal alloys and wears differently. Every oil 
with its additives is different. You need several tests to establish a 
database for your particular engine/oil/operating conditions. Even then 
you may not get a hint of something wrong. We used to have the oil from 
our little diesel analyzed every year. We were still rudely and 
unexpectedly surprized to have the piston rings seize in the piston ring 
grooves. The oil analysis didn't predict that failure. 

    Thanks Alan, i was not aware of what the oil ananysis did.
    
    How about listing some of the other tests you think would
    help..
    
    JIm

	Moved by moderator
        ------------------
    
              <<< VICKI::SIE$DATA1:[NOTES$LIBRARY]BOATS.NOTE;1 >>>
                                -< Powerboats >-
================================================================================
Note 1071.0                         Need Help                            1 reply
MUKTI::TURBAYNE                                      37 lines  12-JUL-1993 10:26
--------------------------------------------------------------------------------
    
    
       I've got a problem with my boat. It's driving me nuts, so any ideas
    will be appreciated......
    
    Specs: 1985 SeaRay 270 with 330 Mercruiser TR package with 400 hours
           (always meticulouly maintained)
    
    
    The problem: Engine starts right up runs well....full power is great
    and when up on plane it runs well at 3400......When throttled back it
    will start "stumbling"....like a bad spark plug or something. It's
    intermittant, more when the boat is warmed up, but also happens cold.
    The stumbling occurs 1500 to 2500 RPM as a rough idea as to RPM.
    
    What's been done to troubleshoot:
    
    On the elctrical side... The following have been replaced......
    .plugs, plug wires, rotor/cap, coil (old one
    had a small crack which would eventually cause a problem), distributor
    sensor pick up and sensor. Swapped the power pack too. Still have the
    problem. Changed plugs again. The plugs look fine when removed. Timing
    is right on the mark. Checked the distributor for bearing wear, and
    there is just the slightest bit of slop, and given this does not have         
    points, this does not appear to be the problem
    
    
    On the gas side: New fuel separater/ carb filter at the beginning of
    season. Also have cleaned idle screw adjustments and re-adjusted the
    carb.
    
    
    
    This is driving me nuts.......Any ideas??????
    
    
    steve

	Moved by moderator
    	------------------
    
              <<< VICKI::SIE$DATA1:[NOTES$LIBRARY]BOATS.NOTE;1 >>>
                                -< Powerboats >-
================================================================================
Note 1071.1                         Need Help                             1 of 1
USCTR1::BORZUMATO                                     4 lines  12-JUL-1993 10:53
                             -< maybe, maybe not. >-
--------------------------------------------------------------------------------
    
    bearing wear of .005 is too much.
    
    JIm

    
    I had a similar problem one time with a 260 Mercruiser, Quadra-jet
    carb. It seems that the metering rods were screwed up in the carb. Took
    it to my trusty marine mech and he fixed it. 
    
    Has the gas been in the boat for a long period of time? some folks are
    finding that the gas now a days is lousey..  no shelf life and full of 
    crud.
    
    Bob

    There was a long discussion on 'modern' gasoline a year or so ago.  The
    concensus was that one should run 'PREMIUM' gasoline in two strokes to
    help reduce ping and improve performance.  I too have experienced the
    short shelf life problem
    
    Jeff

    
    The tanks were about 3/4 full during the winter storage. Also put in
    stabilizer. I also use high grade gas and have probably burned off all
    the old stuff by now. By metering rods, do you mean the "idle
    adjustment screws"??????   The carb is the only thing we haven't torn
    into other than removing/checking the idle adjustment screws then
    re-adjust.  My friend wants to do a compression test before we go any
    further, just to rule that out. I'm leaning towards the carb though....
    
    
    steve

    
    The metering rods are attached to the upper potion of the carb. They
    are not the adjusting screws. They meter the flow of fuel to the inner
    fuel chambers. If you now someone who is familiar with quadra-jet carbs
    ask about them. 
    
    If the carb has not been touched, I would probably go for a carb
    rebuild. the seals on the accelerator pump can also cause intermittent 
    problems. They have a tendency to dryout after awhile and cause
    pressure loss.
    
    Bob

    The metering rods are attached to the upper butterfly for the rear
    throttle port. The secondaries are operated by a combination of vacumn
    and a diafram valve (mounted the side opposit linkage). When the body
    (lower) butterfly valves open from the linkage, a vacumn is subjected
    to the upper buterfly valve. These in turn lift 2 rods out of fuel
    metering jets located in the rear fuel bowls allowing the entry of
    fuel. It's possible that some dirt is lodged in the jets preventing the
    rods from re-seating when y ou pull the throttle back and remove the
    vacumn fromthe upper butterfly. A more logical possibility is a
    defective vacumn diafragm either leaking or binding. You can check this
    by removing the linkage (1 rod I think) from the valve to the upper
    secondaries. Then you can actually operate the rear butterfly by
    pushing on it with your finger (raising and lowering the metering
    rods). Removing the top of the carb to inspect the rods and seats is
    not difficult if you want to visually inspect for obstruction and you
    should be able to do this without removing the carb from the engine.
    
    I don't know what result you will get on a boat but I ran my GTO years
    ago like this to get more punch under open throttle.