Conference vicki::boats

    P. S. - There was also fishing line fouled up inside the propellar
    - could this cause such a problem?
    
    Bill

    Bill,
    	The fishing line could definitly cause overheating. I doubt
    if weeds clogging the input holes could be the reason. Weeds can
    clog the holes but that should be obvious. They usually drape
    themselves over the holes and you just have to remove them to fix
    the problem.  You stated that the problem occurred on two occasions
    I doubt if the weed problem would repeat itself without you noticing
    it. Mud is another possibility but I think the prime suspect is
    the fishing line. When it wraps like that it binds up the prop and
    shaft causing the engine to work like hell, thereby overheating. 
    	I suggest that you remove the prop and make sure that no line
    or other material is left on the shaft; then examine the intake holes
    and if they look clear, put the prop back on and fire up the engine
    using a garden hose with an earmuff type nozzle (or immerse the lower 
    unit in a barrel of water). You should be able to determine if the
    problem still exists that way before you bring it in and spend the big 
    bucks. If the problem still exists then there is a good possibility
    that the mechanic either installed faulty parts or did something wrong
    when he was servicing it. 
    Paul                     

    Addendum
    	While you have the prop off examine the seal on the lower unit
    to make sure that the line did not damage it.
    

    
    
    There's another possibility. The riser on top of the water cooled
    manifold has a habit of scaling up. When the scale breaks loose
    it plugs up the small water passages in the riser. I know, because
    I had to replace mine last year. I have a 17ft. Sea Ray with a 
    120 hp Mercruiser.
    A mew riser from a Mercury dealer goes for about $90, but ther's
    a company in Saugus called Holt that sells Osco risers for $78.
    Good Luck!
    
    
                            ISM         

    I'm not sure I agree that the fish line would cause a
    problem, but it should be fairly easy to check the cooling.

    As .2 suggested, with the boat on the trailer, hook up a
    garden hose to the outdrive with 'ear muffs'.  Turn on the
    water.  You may have some water spraying out a bit.  Start
    the engine.  (Keep the engine speed below 2000 rpm, or you
    can burn out the pump impeller.)  You should have a good flow
    of water out through the bottom center of the prop.  (This is
    with the engine in neutral.  The pump should be turning
    whenever the engine is running.)  If you don't, you've got a
    problem.  The possibilities are 1) the water pump impeller
    was incorrectly installed (there's an easy to drop drive key
    -- perhaps that was left out) 2) the intake is somehow
    plugged   3) scale, sand or other junk has plugged some of
    the other cooling passages.

    I'll check my service guide tonight and see if it offers any
    additional clues.

    For some added commentary, whoever designed that outdrive
    should have their head put in a vise until they rethink the
    location of the pump impeller.  Imagine trying to make an
    emergency repair to it in the water.  Good luck...

    Also, Boat/US can obtain OSCO heat risers and manifolds for
    you at 10% off list price.

    	- Lee

    Bill,
    I have a Mercruiser 120 and had a similar problem . What went wrong
    was---a "mechanic" did the winterizing and ran the engine out of
    water to fog it WITHOUT a water "Muffin" attached and feeding water
    to the lower unit! The main water pump is the one in the outdrive.
    The pump on the engine is for circulation only and can't pull water
    up from the intake on the outdrive. With a good impeller/pump in
    the outdrive, you can burn it out in 30 seconds by running without
    water going into the intake!!!
    
    Did you by chance run it out of water (or some mechanic)??  Fishing
    line in the prop area shouldn't give you any grief with the pump.
    they are in seperate chambers of the outdrive. Weeds should not
    cause a problem either. The intake holes are on the side of the
    outdrive and any motion of the boat would clear them easily.
    
    I suspect running out of water is the problem.
    
    Don

    Thanks for the replies. I had run the boat in the water (in neutral)
    and it still had the problem. I took the prop off, and took out
    the fishing line, and the seal was OK. I ended up bringing the boat
    back to the mechanic, and hope I don't get soaked! What is really
    strange (!?) is that this was the first time in the water, and
    supposedly it was checked out at the shop before they let it go.
    
    I never run the boat dry (without the muffs) so that shouldn't be
    a problem.

    The manifold and heat riser aren't any more than 5 years old.
    
    One other thing, the mechanic informed me that when he installed
    the water pump, that he couldn't find a salt water one, so he put
    in a fresh water pump - said it shouldn't be a problem.
    
    I hope it's not!
    
    Well, thanks again. By the way, if there are any recommendations
    for mechanics in the Worcester area, that might be more convenient
    for me than where I moor it, which is in Rhode Island.

    Bill

re: < Note 60.7 by NRADM::KARL >
    Bill,
If the impeller was a genuine Mercruiser part and the impeller 
failed not due to no water then I believe that Mercruiser will 
stand behind all repair costs. That is why it makes sense to 
repace the impeller every year as there guarantee is good for 
12 months from install date.
norm

    About two weeks ago I was running my 17 footer on Lake Messabesic in
    N.H.   The engine is a 1978  25 Hp  Johnson.  I rarely run it wide open
    but this time we had it at full throttle for a minute or two. All of a
    sudden the engine shut down..... stopped from full throttle.... not
    instantly as in siezing up but as if I shut the ignition off.  Opening
    the cowl revealed that the engine was smoking hot!  It was not siezed,
    it turned over easily with the pull starter.  I allowed it to cool
    completely and test ran it later and it started right up with cooling
    water flow ok.  Further tests revealed that ONLY at full throttle and
    with a corresponding high boat speed the engine lost cooling water
    flow.  A heavy load in the boat with the engine at full throttle does
    not produce cooling water loss.  Back off on the throttle to 95 percent
    and the cooling water resumes.
    
    Questions:
    
    Does anyone know if 78 Johnsons (25 Hp) have an overtemp device which
    shuts down the engine upon overheating?  That is what seems to have 
    happened... good thing too otherwise the engine would have been ruined.
    
    There was NOT any silt or weed blocking the cooling water intake, I
    looked and we had not been in shallow water... only deep mid lake
    water.
    
    I surmise that hydrodynamics/caviation effects at high boat speeds
    cause turbulence which causes the water pump to loose suction.  The
    cooling water flow is FINE under all conditions except high boat
    speed.
    
    Any comments/thoughts on this, or has anyone had similiar experiences?
    
    Jeff

Hi Jeff,
I dunno about any kind of automatic shutoff for overheating, it's 
certainly possible.  My Johnson 88hp has an alarm that sounds, it 
could just as easily be wired up to kill the ignition rather than
sound an alarm.

Since you say it only happens at full throttle, it does sound like
you've got some kind of turbulence or cavitation problem that's
causing the water intake to suck air instead of water.  It shouldn't
be anything you can't resolve, since a 25hp motor on a 17' boat 
obviously isn't producing such blazing speeds that the whole transom
is out of the water.  8^)

First I'd check the mounted height of the motor.  The cavitation
plate should be about an inch or two below the keel - this will 
keep the water intake below the surface even at "high speed". If
this looks ok, have someone else drive the boat at full speed while 
you hang over the transom and see what the situation looks like.
The lower unit should be below the surface and in fairly "solid"
water.  If you see a lot of turbulence or air passing the motor
look for obstructions on the hull that might be causing the dist-
urbance.  Keep in mind that your extra weight over the transom may
bring the stern down far enough that it pumps water normally during
your test. Under normal conditions the stern will probably ride a 
bit higher than while you're hanging over the back.

If everything still looks OK, I'd pull the lower unit off and check
the water pump.  What often happens is that the pump housing becomes
pitted inside.  When this occurs, the pump works ok under ideal conditions,
but cannot pump under high turbulence or when there is a lot of air
mixed in with the intake water.  Since the motor is 13 years old, it
could easily be due for a pump impeller and housing if it hasn't been
done recently.  I've done a couple recently, the cost of the complete
kit from OMC is about $40.  I wouldn't recommend starting the job if 
you plan to take the boat out the next day.  It's an easy job but usually
takes longer than you plan because the retaining screws for the pump
housing almost *always* snap off and need to be drilled and heli-coiled. 

Rick

    
    Just a note to second the motor height theory. As you speed up the
    back of the boat rises pulling the lower end up. I suspect that
    at full speed the lower end is not deep enough to drink all the
    water it needs to keep cool. Lower the engine an inch or two and take 
    it out for a spin. It should be fine.
    
    Doug.

    The water pump impeller was replace a year ago. In fact the whole
    engine was rebuilt... no rings, oversize bored cylinders, new pistons
    etc.  The water pump has always been a bit pickey about the cooling
    water intake dynamics.  For example rabbit ears (when testing) out
    of water do not produce appropriate water which the pump can pick up.
    The water intake is a small screen on the side of the exhaust tube
    which sticks down below the cavitation plate.  When I put a cup shaped
    dealer supplied attachment to fit THAT style of water intake the pump
    did not pick up the water.  With the entire lower unit burried in a
    water barrell its happy.... plenty of water flow.  
    
    My local small engine guy says rebuilding the water pump is tricky.
    I don't know if he's drumming up business or whether it really IS
    tricky enough so a competent (but non professional) guy like myself
    can reasonably handle it.  I can do anything from pulling a car
    engine/clutch to brakes or a car with few problems... so I am no
    dummy mechanically.  What trips me up usually is a lack of special
    service tools or lack of a service manual which I do not have for
    this engine... that is the manual.
    
    What do you think... is this beyond my scope... Just your opinion
    on this... 
    
    Tx. Jeff
    

    Another thing... the transom IS completely out of the water at high
    speed.  That is, the water comes off flat at the bottom of the transom
    even with the bottom of the boat. The engine is a long shaft.
    Yes, your right the weight of an observer WOULD change the engine
    depth.
    
    Jeff

RE: 
>> The water pump impeller was replace a year ago. 
>> For example rabbit ears (when testing) out of water do not produce
>> appropriate water which the pump can pick up.

This could still be the source of your problem if only the impeller
and not the pump housing were replaced.  The key here is that at
high speeds and less than ideal water conditions (air, turbulence)
the pump is unable to pump due to the poor seal in the pitted pump
housing.  A bad impeller alone would likely cause overheating at
any speeed, high or low.  The fact that the motor can't pump water
properly on the rabbit ears tells me that the pump has poor suction.

>> My local small engine guy says rebuilding the water pump is tricky.
   
I don't know if "tricky" is the proper term.  Anyone with some mechanical
ability and patience can do it.  If it weren't for the possibility of 
stuck or corroded bolts it would be one of the easiest jobs you could 
ever do.  It goes something like this:

1) Remove the access cover on the mid-housing and disconnect the internal 
   shift linkage.
2) Remove the (4 or so) bolts which secure the lower unit.
3) Drop the lower unit.  The shift linkage, water tube, and driveshaft
   should all slip apart.
4) The water pump is attached to the top of the lower end.  Remove the
   4 retaining screws.  Here is the only tricky part - if they snap off
   you'll need to drill, tap, and helicoil the holes.  Time consuming 
   but no real big deal.
5) Clean up the area where the pump mounts and install the new stainless
   plate supplied with the pump kit. Insert the impeller into the new 
   housing, taking care to point the vanes in the right direction. Viewed 
   from the top the impeller rotates clockwise.
6) Secure the new pump housing to the lower end, antisieze compound on
   the threads will make the job easier next time.
7) Depending on the engine type, the driveshaft either came out with the
   lower end or stayed in the crankshaft.  In either case, there's a small 
   pin sticking out of the shaft which drives the water pump.  Make sure 
   the original is still there, or remove it and install the new one supplied 
   with the kit.
8) Reattach the lower unit to the motor.  Take a lot of care to make sure
   that the water tube, drive shaft splines, and shift linkage all line
   up and attach properly.  It's a good idea to grease the splines too
   while it's apart.
9) Bolt everything up, secure the shift linkage and access plate and check
   for proper shifting, check the lower end oil (while it's on the workbench
   is a good time to change it) and fire it up!  Check for proper water
   flow, and you're all set for a few more years.


RE: 
>> Another thing... the transom IS completely out of the water at high
>> speed.  That is, the water comes off flat at the bottom of the transom
>> even with the bottom of the boat. 

This is normal.  What I actually meant by "transom out of the water" was
like you see in pictures of race boats, where the entire hull is airborne
and only the prop is in the water.  You think you've got water pickup 
problems?   8^)   Obviously your boat isn't doing that, the lower unit is 
still fully submerged, which is why I think it's more of a suction problem 
that your motor has.

Let us know how you make out!

Rick

<>> The water pump impeller was replace a year ago. 
<>> For example rabbit ears (when testing) out of water do not produce
<>> appropriate water which the pump can pick up.
<
<This could still be the source of your problem if only the impeller
<and not the pump housing were replaced.  The key here is that at
<high speeds and less than ideal water conditions (air, turbulence)
<the pump is unable to pump due to the poor seal in the pitted pump
<housing.  A bad impeller alone would likely cause overheating at
<any speeed, high or low.  The fact that the motor can't pump water
<properly on the rabbit ears tells me that the pump has poor suction.
    
    Not exactly. A good seal between the impeller fins and the housing is
    not what makes the pump go. 
    
    The water should be forced into the lower end at speed - not sucked 
    up from the pump. As the speed of the pump increases the impeller fins 
    bend inward away from the housing under the pressure of the water. As 
    long as the pump is primed this pressure will be maintained. 
    
    At idle the lower end should be low enough into the water as to have 
    an ample supply of water up to or above the pump housing providing a 
    method of priming the pump. Once primed the pump should 'suck' water 
    if there is an ample supply in the lower housing. Once the water is 
    replaced by air the pump needs to be primed again.
    
    The lower end should be low enough that at full plane there is an ample
    supply of water 'forced' into the lower end to keep the pump primed.
    If the motor is to high then air will always get in and foul the prime.
    
    If the rabbit ears do not provide enough water (assuming adequate
    pressure and minimal leaks) for the pump to do its job then you may 
    have an obstruction or a broken fin.
    
    Doug.
                                    

RE: Note 60.15 
>>  The water should be forced into the lower end at speed - not sucked 
>>  up from the pump. 

Doug,
I agree with everything you said about the pump priming itself when
being submerged in the water etc...  But my *experience* also tells
me that a *good* pump will prime itself and pump plenty of water on the
muffs.  The fact that it will pump properly when submerged while stopped 
or at low speed, but has a problem pumping both with the muffs and at 
high boat speed, tells me that the pump is working marginally at best.

It could be a worn impeller, a pitted or corroded housing, or possibly
even clogged tubes although that's doubtful.  Now that I've thought
about it a bit more, I'd pull it apart for a look-see no matter what.
Since the pump ran dry enough to stop pumping and overheat the motor, 
the impeller vanes could be wiped out or well on their way to failure.  
It could be that when it ran dry there was enough water to at least 
lubricate the impeller, but who knows for sure?  Anyone who's ever seen 
the results of a water pump that's been run dry while the motor overheated
knows it ain't a pretty sight (Reg, can you vouch for me on this?).

One other thing Jeff; has this motor been run dry AT ALL since the pump
was put in?  A lot of people think they can run it out of the water for 
a few minutes as long as the motor doesn't overheat.  Not true!  I've seen
an impeller completely destroyed after only about 10 seconds of running
dry on an engine stand.

I'd pull it apart and check it, just for peace of mind if nothing else.

Rick

>But my *experience* also tells
>me that a *good* pump will prime itself and pump plenty of water on the
>muffs. 

    The muffs should be sufficient to fill the lower end and the pump.
    Once primed the pump should do the job.  If there is insufficient
    water pressure to fill the lower unit up to the pump (either from the 
    source or as a result of leaks or restrictions) then the pump will not 
    work. If there is insufficient pressure to keep up with the draw from the
    pump the pump will loose its prime and will not pump again until the
    pump fills with water (a vicious cycle if you can picture it :-)

    The pump won't prime itself under any circumstances. The water has to
    be in the pump before it will prime. Else all you have is a spinning 
    impeller.

    The walls of the pump need not be smooth as it only provides a normal
    force against the water which helps to build up pressure. A rough surface
    will cause the impeller to wear more quickly but will not prevent the
    pump from working.

    As for being tricky, the tricky part is taking off and putting on
    the lower end. Else the pump is a piece of cake.
    
    To answer a previous question: If you can replace a clutch on a car 
    you will have no problems opening up a water pump.

    Can the motor be lowered any on the transom?
    
    Doug.

                            -< From experience ... >-
    
    I can't do a test with the muffs at my dads house because his house
    has low water pressure (makes for a lousy shower too).
    
    
    Doug.

    Ok guys, yes the motor ran dry when I attempted to cool it with the
    muffs.  I didn't intend it to run dry but the muffs didn't work so the
    result was that it did run dry.  I ran it just long enough to see if it
    picked up water (about 10 seconds) or not. When it didn't I immediately
    shut it off... but your point is well taken... since it didn't pick up
    water it did run dry... maybe long enough to ruin the impeller.  
    Incidentally this engine doesn't use muffs I used the wrong term.. the
    water pick up is a screen on the side of that 45 deg. angled exhaust
    tube below the cavitation plate.  So the attachment was an angled 
    plate which wrapped around the tube/screen.  It didn't pick up water
    even though I had the hose on full.... water was squirting out of 
    various holes in the lower unit... screw holes.... shift plate cover
    plate edges etc. it still didn't pick up water.  When submerging the
    entire lower unit in a barrell INSTANT water flow.  
    
    I agree I must take a look and see what is going on in there. Is the
    inlet to the pump a pipe to the screen... or maybe that pipe to the
    screen is missing and the pump pulls water randomly from the filled
    lower unit... that is what seems to be what works... and it explains
    many of the symptoms.
    
    Thanks for the help..
    
    Jeff

    
    NA!	No pipe. The pump sits low enough that it just licks up the 
    water from the lower unit. The hollow cavity in the lower unit is
    designed to hold a minimum amount of water to satisfy the draw of the
    pump.
    
    It really sounds as though you get adequte flow except at full plane.
    If that is the case - if it is possible to lower the moter on the
    transom - that should remedy ht e suituation. There may be nothing at
    all wrong with the pump (which would be my guess).
    
    Doug.

RE: Note 60.19 
>> I ran it just long enough to see if it picked up water (about 10 seconds)
>> or not. When it didn't I immediately shut it off...

>> It didn't pick up water even though I had the hose on full.... water was 
>> squirting out of various holes in the lower unit... screw holes.... shift
>> plate cover plate edges etc. it still didn't pick up water. 


I guess Doug and I will have to just agree to disagree.  Since you mentioned
that you had water coming out of the shift access plate, I still think it's 
a pump problem.  The shift access plate is *ABOVE* the water pump, which means
the lower end was filled with enough water to submerge the pump, yet it still
wouldn't pump.  There should been at least *some* amount of water being pumped
at that point.

It'll be interesting to see what the resolution is.  Be sure to let us know!

Rick

    And if you want to eliminate the muffs as a variable, get yourself a
    nice big bucket to dip the engine in.  I use a large plastic tank from
    my DIY store - it's a header tank that would go in your loft.
    
    Ken
    
    p.s. - allows you to flush more quietly
    	 - plus makes a great drip catcher for drying wetsuits

    The pump always works ok if the lower unit is submerged in a
    barrell/bucket to the horizontal fin on the lower unit.  Whenever the
    unit is physically out of the water but with various muffs/cuffs etc to
    try and inject the water into the lower unit it never picks up water. 
    
    I had the boat out again this weekend and run it several hours on Squam
    Lake.  I had my remote cooling water tell tale right up by the steering
    console so I could watch cooling water flow on an instantaneous basis
    at various load/speeds.  The tell tale hose is an extra hose plugged
    into the tube that squirts cooling water out the side of the underbody
    of the power head so one can visually tell (IF YOU STARE CONSTANTLY AT
    THE ENGINE TO THE REAR WHILE CHARGING AHEAD AT FULL SPEED IN FORWARD) 
    whether you have water flow.  Anyway, I found that there was
    substancial flow under all conditions EXCEPT, ocassionally when at 
    full speed forward with a light load in the boat.  When at full
    throttle with the boat heavily loaded with camping gear no problem full
    flow...  So engine load had no effect on flow... BOAT SPEED did.  Oh,
    here is another thought.... maybe its not speed... under heavy boat
    load the lower unit must have ALSO been submerged deeper because of the
    weight in the boat... ah, the light dawns... it still points to the
    damm pump, or water flow dymanics.
    
    I am reluctant to pull apart an engine which is working fine early in
    the season when all I have to do is back off on the throttle a hair to
    insure water flow.  I would hate to spend the balance of the summer
    waiting for parts, or a pro to bail me out of something I screwed up
    pulling the lower unit apart...  in the Fall no problem, apart it
    comes. 
    
    Jeff

    
    
    >substancial flow under all conditions EXCEPT, ocassionally when at 
    >full speed forward with a light load in the boat.
    
    ... when the motor is highest out of the water
    
    >When at full
    >throttle with the boat heavily loaded with camping gear no problem full
    >flow...
    
     Which tells us the pump works fine ...
    
    >  So engine load had no effect on flow... BOAT SPEED did.  Oh,
    >here is another thought.... maybe its not speed... under heavy boat
    >load the lower unit must have ALSO been submerged deeper because of the
    >weight in the boat...
    
    Yup!
    
    > ah, the light dawns... it still points to the
    >damm pump
    
     A leap into the twilight zone ...
    
    >, or water flow dymanics.
     
    Bingo!  The higher the motor the more AIR (agitated with the water)
    gets into the works.
             
    The pump is fine.  If you can lower the motor just an inch you will
    have solved the problem. If that can't be done then an extention
    may have to be added (longshaft) to insure the lower end is low 
    enough to gather water (instead of air) at full plane.
    
    Doug.

    Its a 20 inch transom which according to the marine I bought the boat
    from requires a long shaft engine.  The engine IS a long shaft.  I
    don't like the idea of cutting the transom down to lower the engine
    because:
    
    1. It changes the aesthetics of the appearance of the boat... it would
    look 'funny' with the transom cut down.
    
    2. More importantly it would reduce the transom freeboard! and set me
    up for getting pooped.  I can't believe how low to the water some of
    the bassboats I see are... how do they survive in a seaway?  I guess
    the answer is they don't go out in rough weather.... I do though.
    
    3. It sets the power head of the engine up for getting wet by being
    closer to the water. 
    
    Guess I will have to find another way to fix it.... either replace the
    pump or as I currently am by paying close attention to the tell tale
    when running at high speed.  I usually cruise at 2/3rds throttle so
    I don't beat on the engine... 2/3rds is no where NEAR the cooling 
    water cut off point.  95 % open is near the cut off point.
    
    Thanks for the help.   Jeff

Well, this might give you more of a confusion factor, but I gotta share
something I learned last year.

My engine was pooping out, but only after a moment at full throttle.
Several mechanics threw up their hands after replacing parts. Get this:
it ran absolutely fine in a test tank.

This is a Johnson 235. Yeah, a different model from yours, but many of
the same principles are used in the engines.

To make a long story short, when you reach full throttle with my engine
(and many more) there are pressure relief valves that open and divert the
cooling water into a different path. My engine has one of these valves on
each bank, just above the thermostats. The valves are spring-loaded
rubber flaps that look slightly like exhaust valves in a 4-cycle engine.
My problem turned out to be caused by the springs that load the valves
being completely encased in crystalline salt (precipitated out of sea
water over a period of five years or so), preventing the valves from
operating. 

I'll be truthful; I haven't fully decided whether the salt prevented the
valves from OPENING or from CLOSING. I cleaned out all the salt, which
was over a heaping tablespoon in each valve, and that finally fixed a
problem that had plagued me for two seasons.

I don't know what happened to the tell-tale water ejection when the
engine would "act up" - I never happened to look at it (this is on a 24'
boat, and some things are just harder to look at, particularly at full
throttle).

Art

    Interesting solution Art.  A couple of BIG differences though between
    our applications.
    
    1. My engine is virtually never run in salt water, and when it rarely
    is its always flushed immediately after.
    
    2. Your engine I assume was a V engine with 4 cylinders and a
    significantly different cooling water arrangment. My engine is less
    complex, and, I believe doesn't even have those diversion valves.
    
    I have clear tubing which the tell tale water flows through.  At full
    throttle I DO NOT see bubbles flowing thorough the cooling water just
    prior to a diminished flow of cooling water.  The flow just tapers off
    and stops over a period of several seconds.  At that point I back off
    on the throttle and the flow immediately resumes.  This suggests that
    air being incorporated into the cooling water intake is not the cause
    of the stopped flow. 
    
    Maybe is a result of 'suction' in the lower unit due to the flow
    dynamics which places negative pressure in the lower unit which
    overcomes the pump suction?  This points to a marginal pump.
    
    Jeff
    

    I just thought of one other possible source of your problem,
    although fairly unlikely.  Since you mentioned that someone
    put in a new water pump impeller last year, it's *possible*
    that they installed the pump backwards.  That is, with the 
    vanes facing in the wrong direction.  It can go in either way 
    but only works properly in one direction.  I've never seen it
    happen so I can't say for sure what the result would be, but 
    it seems possible that the force of the water coming in at high 
    speed or high pressure could force the vanes away from the pump's 
    machined outer surface, causing water output to suddenly stop.
    As you slow down pressure would fall, and the vanes would once 
    again contact the housing, and flow would resume.
    
    If/when you pull it apart, check to be sure it's in right, don't
    just reinstall the new impeller the same way as the old one. If
    you look at the pump housing from the top, the impeller rotates
    clockwise, and the vanes should be bent back so that their tips
    "follow" the base.   To install the impeller, put a little grease
    inside the housing.  Then, looking at the housing from the bottom,
    the impeller should be rotated into the housing in a counter-clockwise
    direction.
    
    This is probably a longshot, but if this is the "fix" then you
    owe me a boat ride and a beer!
    
    Rick

    >I have clear tubing which the tell tale water flows through.  At full
    >throttle I DO NOT see bubbles flowing thorough the cooling water just
    >prior to a diminished flow of cooling water.  The flow just tapers off
    >and stops over a period of several seconds.  At that point I back off
    >on the throttle and the flow immediately resumes.  This suggests that
    >air being incorporated into the cooling water intake is not the cause
    >of the stopped flow. 
    
    Water pumps are not air tight - nor do they prime themselves. This is
    why you won't see air bubbles in the outflow. Once the pump is unable
    to pick up water from below the pump housing the water above the pump
    will slowly drain down back into the lower unit (yes, even even with
    the pump spinning) until the air is displaced by the water. Then the 
    pump will start pumping again.
    
    I wouldn't expect you to cut the transom to lower the engine. That is why
    I ask 'if' it could be lowered any. 
    
    >Maybe is a result of 'suction' in the lower unit due to the flow
    >dynamics which places negative pressure in the lower unit which
    >overcomes the pump suction?  This points to a marginal pump.
    
    The water intake holes are designed to maintain positive water pressure
    at speed to assure proper supply to the pump. Only lifting one or
    more of them out of the water flows path will result in reduced
    pressure in the lower unit. 
    
    Lets try a different approach ...
    
    Is this an aluminum boat?
    Is there an adjustable motor angle bar (usually 3 to 5 settings)?
    If it is adjustable what postion is the bar in?
    
    In the meantime keep all the heavy items in the back of the boat :-)
    
    Doug.
    

    RE: Rick -
    
    >put in a new water pump impeller last year, it's *possible*
    >that they installed the pump backwards.  That is, with the 
    >vanes facing in the wrong direction.  It can go in either way 
    
    Even if the vanes were installed in the wrong direction they would
    quickly 'flop' over to the right direction at full throttle.
    The vanes don't actually touch the pump walls when pumping water
    at high revolutions (read: vanes flex inward under pressure).
    
    Doug.

    To answer your questions:
    
    I suppose its possible the impeller is in backwards... opening the unit
    will answer that question... but since it was installed by a pro I
    expect that backwards impeller installation is unlikely but not
    impossible of course.
    
    Another factor... it may be ENGINE RPM which determines the water flow
    failure.  Of course low boat load with wide open throttle would
    translate to high engine RPM relative to a heavy boat load with wide
    open throttle. 
    
    The engine is on a wooden boat.  Yup wooden... a real classic in good
    shape too.  Yes the engine has an adjustable tilt angle. Its set some
    where in the middle of the tip range to keep the bow at the right
    angle.  Yup I can change the tip angle to see if it affects the water
    flow.... but as Rick has suggested its time to stop debating it, open
    the lower unit up and find out what is going on.  
    
    Since I never had this problem last summer (no water flow at speed)
    and the boat/engine relationship has not been changed it suggests that
    something has changed in the engine... (probably a worn impeller).
    
    I mentioned in an earlier note that I DID start it up dry in the 
    Spring to try and get the muffs to work... they didn't work and the
    result was that the pump unintentinally got run dry for 10 to 15
    seconds.  Since the engine had been sitting it probably was DRY and
    not even damp in there thus NO impeller lubrication for those 10
    seconds.  
    
    Guess I will have to "bite the impeller" and open the damm thing up. 
    
    Jeff

    Moved by moderator...
    
================================================================================
Note 384.5                  WATER PUMP MALFUNCTION???                     5 of 5
SALEM::GILMAN                                        25 lines   2-JAN-1992 09:10
                                -< Water pump >-
--------------------------------------------------------------------------------
    I can't remember the string I entered my note in back last May.  I had
    an intermittent water flow problem on my 25 HP Johnson.  Remember the
    incident where I lost cooling water at high speed only but as soon as
    I backed off on boat speed cooling water flow resumed?  Anyway I pulled
    the lower unit off yesterday. The pump impeller appears a bit worn..
    nothing heavy duty but things were not pristine in there.  There was
    some corrosion between rotor and housing but the boat has just been
    sitting for 2 months. (Yes it was flushed with fresh water), in fact
    its least run was in Lake Winni in early Nov.  No sign of clogged 
    passages or sheared key between prop shaft/impeller.  So, I assume
    we are dealing with a marginal impeller.  Also I noted when running
    the engine wet in a barrell over the summer that the pump WOULD NOT
    pump unless the pump housing was COMPLETELY submerged in the water
    in the barrell.  Are these pumps supposed to be at all self priming?
    That is should it pick up water a few inches down from the height
    of the impeller or is having to have the impeller immersed in water
    for it to pump normal?
    
    Are there any tricks I should be aware of upon re-assembling this unit?
    Tricks to help line up prop shaft, shift linkage, and 
    cooling water pipe all at the same time?  Any hints would be much
    appreciated.  I can see why one must NEVER run a dry impeller in an
    outboard.... heat and scoring would result in SECONDS.
    
    Thanks,  Jeff

    I think I have the explanation of the water flow cut off now. Its
    simple... the impeller is somewhat scored and the pump can't pump if
    its forced to pull a suction.... in fact the pump body has to be
    several inches UNDER WATER for it to pump at all... when the boat is
    at speed the level of the water is parallel to the bottom of the 
    boat at the transom... this forces the pump to pick up water from
    a lower point that at lower speeds.. thus the pump looses suction and
    I loose cooling water.  The fix?  Replace the pump.  I am trying it
    and we will see.
    
    Jeff

    I looked for another waterpump note but couldn't find one.  This note
    is close so I'll ask my question here.
    
    I have a 150 hp Mariner Outboard and I run in salt water.  How often do
    you guys replace the waterpumps in you're engines?  Mine has 1 1/2 yrs
    since the engine was new and I'm wondering if I should replace it in
    the spring.
    
    Thanks
    Gordon
    

    I assume that 1� years translates into 2 seasons of use?  If
    the boat only sees salt water and is never flushed with fresh, 
    it's probably about time to drop the housing and check it.
    
    For boats used in fresh water only, my guesstimate is to check
    the pump every 4 years.
    
    Rick

    re: .-1
    
    The 1 1/2 yrs is two seasons, starting in july the first year.  The
    merrimack is mixed with some fresh water on the outgoing tide, but I'll
    treat it as salt water.
    
    I assume that check it means replace it.  If I have to go thru the work
    of pulling the lower unit (not really that big a deal) I will replace
    the impeller at least, if not the housing also.  Anyone know what a kit
    costs?
    
    Thanks for the input, I guess to be safe I'll do it this spring.
    
    Gordon

    Yes, in most cases "check" translates into "replace" as long as
    it's apart.  Replacing the impeller is pretty much a given, but
    also carefully check the pump housing.  If it shows any signs
    of wear or pitting that should be replaced also.  

    You won't regret doing the first pump replacement early.  It gives
    you an idea of how the pump wears in this particular motor, and
    allows you to get some anti-seize compound on the retaining screws.
    If the pump and housing still look good, you can probably extend
    your replacement cycle out to every 3 years.   
 
    I don't know how much the Merc/Mariner kits are.  OMC stuff is
    about $20 for the impeller, $40 for the complete kit with housing.
    
    Rick

    The YAMAHA cartridge assembly (impeller and all) for a 150 HP costs
    $85.00.  I plan to do mine in the spring and YAMAHA suggests that the
    whole assembly be replaced.  I hear from other YAMAHA owners that the
    shaft splines should be greased prior to putting the lower end back in
    place.  Anyone out there with hands-on experience with the YAMAHA
    outboards?
    
    /MArk
    
    BTW: From what I've gathered in speaking to outboard owners,...it
    doesn't matter wheather you run in salt or fresh water.  The impeller
    will wear according to use and will sustain different degrees of wear
    depending how silty the water is that passes through the engine.

RE: Note 60.38
>> I hear from other YAMAHA owners that the shaft splines should be 
>> greased prior to putting the lower end back in place.  Anyone out 
>> there with hands-on experience with the YAMAHA outboards?
    
This isn't unique to Yamaha, the driveshaft splines of ANY outboard
should be greased with moly grease before reassembly.  I did one 
recently where the driveshaft was literally welded into the crankshaft
by rust. A friend arcwelded a bolt onto the bottom of the driveshaft,
then we used a slide hammer to remove the shaft.  Needless to say I 
had to find another driveshaft...

>> BTW: From what I've gathered in speaking to outboard owners,...it
>> doesn't matter wheather you run in salt or fresh water.  The impeller
>> will wear according to use and will sustain different degrees of wear
>> depending how silty the water is that passes through the engine.

This outboard owner says it DOES make a difference whether you run in 
fresh or salt water. Pump housings run in salt are much more subject 
to wear and corrosion than those run in fresh, although as you said 
silt will also accelerate wear in either fresh or salt.  My wife's
uncle just gave me a 1959 Evinrude 3hp that hadn't run or been apart
in years, but had only seen fresh water.  The pump and housing were 
so clean I just buttoned it back up without replacing them.

Rick

    When reassembling the pump housing and the various bolts which hold
    the lower unit/assy together I assume that greasing or putting lithium
    grease on the bolt threads will reduce the chances of finding siezed
    corroded bolts the next time I want to take it apart to do a water
    pump.  What kind of anti-corrosive/anti-sieze should I put on the
    bolt threads?
    
    Tx.  Jeff

    I replaced the entire water pump on my 25 hp Johnson. Remember I had
    the problem with loss of cooling water at high speed only.  The
    impeller and pump housing was slightly scored. I suspect that was
    enough to cause the problem.  Anyway, I replaced it all and we will
    see if the problem has gone away.  Does anyone know if the typical
    Johnson (OMC) water pump will lift water from the water intake, or,
    are these pumps designed to at least PRIME (at low boat speed) so
    the lower unit is deeply submerged with the impeller under water?
    My rebuilt pump does not seem to be able to lift water until its
    primed... then there is no problem.  By primed, I mean at start up
    the impeller is underwater.  
    
    Your comments about anti-sieze are noted.  I think the  essential
    torque loads and use or non use of thread compounds matter mostly
    in the crankshaft, rod, crankcase half bolt type areas.  Other
    areas of the engine would require common sense tightening IMO.
    
    Jeff
    
      

    
    The discussion about Anti-seize and locking compounds has been moved
    to note number 941.
    
    Rick

    
    
    DO NOT start the motor when the pump is not submerged! NOte 60.59
    indicates that you may be starting the motor when the pump is not
    submerged. This is Guaranteed to take out the impeller- usually by melt
    down. The water lubrictaes the pump as there is considerable friction
    between the impeller and impeller housing when run dry.
    
     Starting procedure is :
     Lower motor into water
     Start engine
    
     
     
     

    I agree... the catch is when using 'earmuffs' to run the engine out of 
    the water, as when flushing salt water out after an ocean run. If
    the earmuffs don't work (don't get water UP into the water pump) as
    happened with my case the impeller was damaged by the time I realized
    the muffs didn't work because it wasn't pumping. The sure cure is to
    use a barrel filled with water.  In water scarce areas of the Country
    (like Calif) this is a water wasteful method of flushing. I live in
    N.H. so this is not an issue... my point is that the muffs save water
    but can be risky on certain engine designs, like mine.
    
    Jeff

    
    
     I can't understand why the miuffs don't work-
    Put on Muffs
    connect to garden house
    
    Even if the water pump is shot, the water pressure from the hose will
    force the water through the pump and circulate through the engine.
    
     Hoope you are not using the muffs and then connecting the hose to a
    bucket and expecting the pump to pull the water through- in that cas it
    will be goodbye pump.
    
    
     I can't understand why the muffs do not work-I've used them to test an
    engine when the pump is shot and I haven't gotten around to replacing
    it. ON mY OMC I/O , which has the same design pump as your O/B,
    whe I connect th muffs up, the water circulates through and sytarts
    trickling out the exhaust a couple of seconds after I turn on the
    water.
    
     Am I missing something?????
    
    Dick
     

    Yes, the TYPE of muffs.  My engine has the cooling water intake in TWO
    places.  One is at the end of the 'skeg' which sticks out at a 45 deg.
    angle below the horizontal 'plate' which limits spray up beside the
    engine.  The other is on the side of the lower unit.  The 'muffs' sold
    for my engine are the older style with a U shape which wraps around
    the skeg... when the water is on it squirts out the OTHER hole so the
    water level never rises in the lower unit to the pump impeller.  Can I
    block the other hole up?  Well sort of... its not exactly a hole... its
    a cover plate which seems intended to leak at the edges.  EACH test of
    the muffs which doesn't work (get water to the impeller) theoretically
    damages the impeller if I start the engine.  It certainly doesn't
    provide enough of a seal (the muffs) to force water through the engine
    up 3 or 4 feet to the power head and out the tell tale.. So the only
    way I can tell is to start the engine and thus risk the impeller.
    
    Jeff

    
    I have a small outboard 8hp. The lower unit has a water pick-up
    (series of slits) my muffs ar U shaped. I connect the muffs
    to the hose, put them on the engine lower unit, turn on the water,
    
    wait a few seconds, maybe 10 or so, start the engine,
    if i don't see water by the count of 3, i shut it off.
    
    There was one ocassion where the water did not stream
    out the tell tale, but dripped, the tell tale got
    clogged with salt, and restricted its flow..
    
    JIm..

    RE: .64
    
    Why not place a piece of duct tape over the lower hole to
    prevent water from being forced out there?  Then just use 
    the muffs on the upper water intake.
    
    Rick
    

    Good idea Rick.   
    
    Jeff

    This is not related to outboards or I/O's but is somewhat relative.
    I saw an add somewhere (possibly Classic Boating Mag) for a "muff type"
    device that must go over the water pick-up on inboard boats.  I know we
    had a discussion somewhere about disconnecting hoses and sucking water
    out of a pail.  I'ld be interested to find out how this device works if
    others are also curious.  
    Wayne

    
    i like disconnecting the hose from the valve, they have a tendency
    to "weld" themselves to the fitting.
    
    the other concern i have, is that the muff arrangement doubtfully
    would suck up the antifreeze from a pail.
    
    JIm.

    There's a "muff" for inboards advertised in the back of Waterski
    magazine. It's called FAKE-A-LAKE but I beleive it relies on water
    pressure from a hose. Doubt it would draw water out of a bucket unless
    the bucket was higher than the water pump [ie on the swim platform or
    higher].
    
    ~jeff

    Well, being the curious one I called the people who are selling the
    "Hydro-Cup" ($25 + $2.50 S+H).  There is a cup with an inlet that
    connects to a water hose.  The cup has an adjustable leg which goes 
    down to the ground.  You place the cup under the water inlet scoop,
    extend the adjustable leg to the ground, and connect a garden hose.
    I asked the lady if a garden hose could supply enough volume of water 
    if you wanted to "race" the engine.  She said they just keep an eye on
    the gages.  For the sake of keeping $27.50 in my pocket, I'll
    disconnect the hose inside the boat and get plastic hose to go to a
    bucket.
    Wayne

    
    	Try using a submergible pump. I use one when I winterize my camping
    	trailer, it works great. I put the pump in a 5 gallon bucket, fill
    	it up with antifreeze, hook the hose to the city or high pressure
    	inlet and turn on the pump. After purging the system of air and 
    	a little into the hot water tank, it is done within a few short 
    	minutes.
    
    	If needed the pumps can be rented at any rental shop for about
    	$ 5.00 a day.
    
    	Good Luck
    
    	Mike

    Maybe I missed something here... but what do you use the submersible
    pump for?!  Whats the application?

    
    it begs the question, why the submersible pump, and what does the
    garden hose do.
    
    i'm lost..
    
    JIm.

re .73 and .74 (re .72)

	I think he was describing how to put a small submersible pump 
(like a sump pump) into about a 5 gallon (donut jelly) bucket and use
it to pump anti-freeze into his camping trailer's water system - the
garden hose going from the pump to the trailer's city water
connection (I think that's what camper/trailer folks call the spigot 
that water goes INTO from the outside of their home on wheels).

	The suggestion seemed to be that the method could be adapted
to force water into an engine that wasn't sucking hard enough through 
the muffs.

DISCLAIMER:  This is pure speculation (-:

	R

    
    there is an easier, based on the prior speculation.
    
    my boat has the following:  water tank, 12v water pump,
    hot water heater.
    
    the process is:
    
    disconnect the cold water supply line to the hot water heater,
    and let it drain. disconnect the other line, and connect these
    two. (you have now bypassed the water heater)
    
    disconnect the line from the water tank, to the pump, 
    and set aside. connect a longer line to the pump,
    and put one end in a gal jug of antifreeze, turn on
    pump open the faucets, one at a time, when the antifreeze
    appears in good color turn of the faucet, do the other
    side.
    
    where the is more than one faucet do the furthest away first.
    
    you could possibly do the same with a trailer, barring any
    unkowns on my part.
    
    city water pressure should be more than a submersible pump
    can deliver.
    
    JIm.

    
    
    	Right on .75......8^)
    
    	The pump connected to a garden hose would draw anti-freeze from a
    	5 gallon bucket and force it through the hose to the engine. 
    
    	Mike

	130 HP, Chevy 4 cyl, Mercruiser I/O. Started the thing up for the 
first time a couple of days ago and got no water circulation out thru the prop.
I assume the impellor that hasn't been changed in recent years is shot.
How tough is is to change?

thanks,

Rick

Yep, outdrives are somewhat foreign to me..... Give me a Velvet Drive anyday!

    
    Is that a 130 HP? I have a Chevy 4 cyl, 120 Mercruiser on which I just
    changed the impeller in this past weekend. I had the out drive off
    in order to change the shift cable so I did the impeller then. Not too
    bad a job with the outdrive off, but I can see it would be a bit of a
    pain putting the lower unit back on with the outdrive on the boat. You
    may want a friend handy. 
    
    5 exposed nuts and 1 allen head bolt under the anode. Mine has an access
    hole in the top of the cavitation plate to get at the allen head bolt
    that holds the  anode on. You can then access the bolt under the anode.
    
    Don't forget to replace the little O ring that seals the gear lube  port
    between the lower unit and upper gear box.
    
    Have fun.
    
    John