Conference vicki::boats

    You might try:

    	Blue Water Books & Charts
    	1481 SE 17th Street
    	Ft. Lauderdale

    	(305) 763-6533

    I'm pretty sure they do mailorder.  If they don't, there's a
    great ice-cream place in the same plaza.

    I'll give them a call.  Does the ice cream place do mail-order, too?
    Thanks, Wayne

    Wayne,
    Ken Hankinson writes a monthly column for Trailer Boats magazine
    (Designer's Viewpoint or something like that).  He also advertises
    his boat plans and blueprints in the back of the magazine every 
    month .  You might try looking up that ad and calling or writing 
    to Ken directly to find out where to get a copy.
    
    Rick

    Rick, thanks for the tip.  I called Ken (Ken Hankinson Associates,
    box 2551T, La Habra, CA., 90631, Tel # 213-947-1241).  He is UPSing 
    the book to me along with a price list of products/plans that they
    carry for boat and trailer building.  They accept plastic money (Visa).
    The book was $18 (plus shipping) but it's a 250 page hardcover book
    which covers inboard motor installations plus how to convert auto
    engines for marine use.  I told him he writes good articles.  Thought
    he'ld give me a price break.  Didn't work.
    Wayne

    Not sure if this is the right place for this, feel free to move it.
    I was wondering if someone out there could help me. How does one
    determine the angle at which an outboard sits in the boat? The reason I
    am asking is the Prop. shaft exits the boat at the same angle. Can this
    angle be changed to inprove the ability of a boat to plane out and
    how can I determine which way to change the angle to improve it.
    Specs of boat follow.
    
    1950 OWENS with original 6 cylinder Chrysler Ace marine engine.
    This boat has a planing type hull.
    Presently running a 12" 9 pitch prop.
    
    This boat just will not Plane out unless the wind and current are with
    me. I am wondering if changing the angle of the prop. to the boat can
    help. 
    
    Did anyone order the book that was noted in previous replies?
    
    Thanks,
    
    Jerry 

    Jerry, I did purchase the book and it is excellent but I'm afraid that
    you may be biting off more than you may want.  It would be hard for me
    to offer advice without knowing more about your boat.  The Owens that I
    am familiar with were relatively large and nothing short of a larger
    engine would get that boat to plane.  Can you give some more info? 
    What type of marine gear do you have?  is it a direct drive or
    reduction?  Is that the original prop size?  Is it in good condition?
    Does you engine rev at WOT to the correct speed?  Is there much space 
    between the tips of the prop and the bottom of the boat so that
    possibly a larger prop/reduction gear may be possible?  I would assume
    that the current prop shaft angle (if still original) was determined to
    be optimum back when Owens designed the boat.  I don't believe (unless
    you are a qualified naval architect) that you will stumble upon a
    better prop shaft angle without many tries.  You are welcome to borrow
    my book which will also be very helpfull should you decide to repower
    which may be the only way to get that boat to plane.  A Chevy small
    block with a Warner gear would probably weigh alot less than the
    Chrysler Ace and give you much better performance and reliability. 
    Save the old engine/gear for later resale should someone want
    originality over performance.
    Wayne  

    Hi Wayne,
          Thanks for the offer to borrow the book, I will take you up on it
    if it is somewhere close.
          To give you some more info.
    13 years ago I bought this boat with the engine and cutlass bearing
    mount removed. It has a direct drive,straight forward/reverse gear.
    I took a look at some similar boats and installed the engine with
    an angle that looked good. It has never planed out, the engine is
    rebuilt and runs great. it delivers a total of 5000 rpms which is
    the top speed of the engine. It just is not enough, now I am wondering
    if it ever was. I have talked to H&H propeller in Salem about it
    several times and they were helpful. They suggested I add a cup
    on the trailing edge of my prop, I had them do it and it seemed to 
    be better but its not what I wanted. Perhaps I should go back to them
    and see if they have any other Ideas. I have to remove the engine
    again this winter so it is a good time to adjust the angle if it would
    improve things.
          I would however like to check out the book. I work in Shrewsbury
    Ma. 
    
    Thanks again,
    
    Jerry
    

If the motor is able to spin up to 5000 rpm but the boat still won't
plane, you've either got too much prop slip or too small a prop. Maybe
both.

Adding a bigger motor at this point wouldn't help, because 5000 rpm
is 5000 rpm, no matter whether turned by a 6 cylinder or a Keith 
Black Hemi.  What you may find though, is that if you find and correct 
a prop slip or pitch problem, the motor may no longer have enough power 
to reach the optimum rpm.

First, you should work the numbers and try to determine what the boat's
actually doing.  The formula for speed is: 
    shaft rpm x prop pitch / 1056.
  
Since we don't know your gearbox ratio, I can only guess.  A 1:1 ratio 
would give:
    5000 x 9 / 1056 = 42.6 MPH

A 2:1 ratio should give 21.3 MPH.  If your ratio is 1:1, your boat should
be really flying at over 40MPH, and definitely on plane.  Since it's not,
I'd have to guess that either you've got some massive prop slip, or your 
ratio is closer to 2:1.  Since a 2:1 ratio gives a *theoretical* speed of
21.3, actual speed allowing for normal prop slip should be around 18-19
mph, which is right in the range your boat should just start to plane.

So I'd say to find out your gearbox ratio, and determine just how efficiently
your boat is working.  If the numbers indicate that there's not much slip
and things are as they should be, you'll need more pitch and possibly more
horsepower to turn it.  If the numbers indicate that prop slip is excessive,
say over 20%, you'll need to work on reducing the slip, by changing the shaft
angle or finding a more appropriate prop.

Hope this helps...
Rick

    Rick,
         You have given some great information here. I am wondering though
    why you formula does not take into accout the weight or hull
    configuration of the boat. Another thing I am not sure of is what you
    mean by prop slip.  
         This has a 1:1 ratio, I am running 5000 rpm's with a 12' prop
    having a 9 pitch with a leading edge cup. According to your
    calculations I should be screaming and definately on plane. 
    Not so unfortunately.
          So now what? I am going to assume that the prop was the one 
    manufactured for the boat. I am turning it fast enough. How if any
    way does the shaft angle play in this? Just thinking about it, if
    I increase the angle, (meaning the angle of the bottom of the boat
    to the shaft giving more room between the boat and prop.) Will this
    tend to push the stern out of the water more, helping it to plane
    out? And what if the angle was to great? What would happen then?
    
    Thanks for helping
    
    Jerry
                        

    	The pitch of the blade is the distance the prop would travel in one
    rotation with no slip.  The problem is that it is impossible to live up
    to that theoretical number.  Many factors come into play that determine
    how much slip is experienced.  Shaft angle, blade tip clearance, blade
    loading, depth of blade under water, flow into blade, etc.  There are
    books on the subject ranging from highly theoretical to very practical. 
    One of my Christmas presents was a very practical book on matching
    propellers to boats.  The title was something like (the propeller
    handbook) it was about $24 or so.  I suggest you borrow or buy a copy
    if nothing else it will help you understand how that critical component
    is working.


    	Back when I was studying Naval Architecture at the University of
    Michigan the joke was it took a really good engineer to design a really
    bad propeller.  One of the great all time designers of large ship
    propellers was a Monk with no training at all.  I remember using a Navy
    program to design propellers it used all the right theories etc.  The
    problem was it would produce designs that could not be cast and
    machined much less hold up under real world conditions.


    Forrest

    
    
    	How big is this OWENS that we are talking about?
    
    	If it's a larger boat (ie: +19') then a 12 inch prop carrying
    a pitch of 9, IMHO is pretty small. For example my 19' Ski Nautique
    sports a 13X13 and later models spin a 14X12 (right Reg?)
    
    Rick

Jerry,
The formula I gave calculates the "theoretical" speed that the prop 
should be moving forward, assuming zero slippage.  It doesn't take
hull design into account.  For more info on prop slip, see note 575.

All boats will have "some" prop slip.  Modern planing powerboats 
generally have around 10% or less, although up near 20% isn't uncommon.
I'm not familiar with the design of your boat, so I don't know what a 
good slip ratio would be. To estimate approximate "real" speed, calculate
the theoretical speed, then multiply it by what you think the slip rate
should be, say .8 or .9.  To calculate "actual" slip, divide the actual
speed into the theoretical speed, them multiply by 100.

Let's say that since your boat won't plane, it's doing under 20mph.
20/42*100=47.6% efficiency, or about a 52% slip rate.  Try working
the numbers with your actual "observed" speed.  I think you'll find
your prop slip is somewhere up around 50%, which is very bad.  What
does it sound like, does the prop seem to be almost freewheeling at 
that speed?  At 50% slip it won't sound right at all, kind'a like
spinning your wheels on ice.

To reduce slip with an inboard, you want to *decrease* the prop angle
to the hull.  In other words, you want the prop facing directly forward 
as much as possible.  Any "upward" push is basically wasted. Compare it 
to an I/O or an outboard, in which the front of the prop actually points 
slightly *downward* to get maximum speed.  Inboards have the prop facing 
the wrong way for maximum speed, so anything you can to reduce the angle 
will help.  How much space is there now between the prop and the hull? 
Is there room to decrease the angle, bringing the prop closer to the hull?
If so, you may want to think about leaving it as is, and trying a larger 
diameter prop.  The 12"x9" prop you're using is pretty small for the load 
you're pushing.

As I said, I'm not familiar with your hull design.  But if its a big
old boat with a round bottom, soft chines, no lifting stakes etc., it's 
possible that it's a semi-displacement hull, and isn't really meant to 
plane at high speed like a modern boat.  Do you know for sure if other 
examples of this same boat are able to fully plane with the same power?
Otherwise, you may be chasing after speed which just isn't feasible with 
your boat.

Rick

re  last few (re screw)

	right !

	ski boats typically run something around a 13x13 with 1:1 
transmission  -  mine turns a 14x16 with a 1:1.23 (bigger screw, 
turning slower).   A year or two ago I did a spread sheet that 
convinced me that prop slip on my boat and (I think it was Doug's 
Maliboo) was close to zero once on a plane.  Now then......

	Think like you're back in calculus 0_01 ....  all that stuff 
about "in the limit, as delta x approaches zero"  a prop with no pitch 
pushes no water, turns very easily and slips (almost) infinitely.
Similarly with diameter, the more of it you have the larger the prop's
area (square function) so the more it can  "bite"  the water (assuming 
it is pitched appropriately against the axis.   Subjectively I'd say,  
"You gotta darned weenie prop thar, no wunder you can spin 5K, 
surprised the motor ain't blowed itself up yet".   I can't see messing 
with installation angle at this point, too difficult and in any case 
its probably impossible to make a significant change.  BTW, the 
standard is 15 degrees - but what if you had 30 degrees ? (-:

	If you have right rotation and a 1 inch shaft we could try my
spare prop sometime, that should show something.  If it still revs to 
5K and doesn't plane errrrrrr,  "tranny slip"  ?  )-:

	Reg

 

    
     Ok, ok, I tried to stay out of this (there's been lots of good replies
    so far but...).
    
      I think that turning that engine up to 5K is a bit asking for
    trouble. With that in mind......
    
      You didn't mention if using the prop after it was cupped brought down
    the rpms? If I didn't (And it should have if all else was right, but it
    sounds like it didn't) I just plain think that prop is WAY too small. At
    least the pitch is too small, and maybe the diameter, but pitch first.
    The rpm limiter may be the engine itself. It may have so little load
    that it is just running up until it gets to an rpm where it simply
    cannot spin any faster, almost no matter what the load. That would
    certainly explain the rpm NOT dropping a little after you had the prop
    cupped. And also why it spins so merrily with such poor forward
    movement.
    
    Also - if this is a planing hull and it is NOT planing, prop slippage
    WILL be VERY high. So we shouldn't confuse that  -  yet.
    
      What size is this boat? How much does it weigh? What Hp is the motor?
      Also, do you have a reasonable idea that the tach is ok? (like close
    to being right? It doesn't have to be perfect - few are)
    
      We could be more accurate in our 'guesses' if we had more info.
    
    				Kenny

    Again, how big is this boat??
    

re  .recent

see
>                     <<< Note 928.5 by JUPITR::CATRON >>>
>                       -< Any inboard guru's out there? >-
>
    
>    1950 OWENS with original 6 cylinder Chrysler Ace marine engine.
>    This boat has a planing type hull.

	From this I conclude that it should plane - i.e. the size of 
	the boat isn't relevant to the question being asked (-:
	{between 15 and 25 ft is my guess - regardless, it came with a 
	fairly big 6 cylinder inboard and its a planing hull, I think 
	it is safe to assume that it should plane with this engine}

>    Presently running a 12" 9 pitch prop.

	the wording suggests that this might be not the original prop, 
	so does the elapsed time (-:    
	This is an eenie weenie prop.  Somehow I don't think it would 
	pull a kneeboarder off a dock start if I put it on my boat (-:

>    This boat just will not Plane out unless the wind and current are with
>    me. I am wondering if changing the angle of the prop. to the boat can
>    help. 

	I think that your opportunities to do this are in any case 
very limited.  Just look at the layout and think about the geometry, 
putting the engine in the BOW would only change the angle a few 
degrees.  If you have enough thrust and the angle is "wrong" you will 
either get lots of  "bow up"  on take off or lots of  "stern lift", 
but it should plane.
   
	re  cupping;

	props  "push"  water,  they also  "spin"  it.  Cupping helps 
to... geee, this is aweful difficult to describe without hand motions (-:

	Try an analogy... fog lights  vs  spot lights of equal power;
think of a cupped prop as being more like the spot light.  It sort of
focuses the spun out water into a tighter cone ,,,  no ?  well, its 
the best I can do right now (-:

	Anyway, if you want to try a prop swap some time call me.
I think your boat will plane out with my prop, thought revs might
limit to under 4K  - -  no need to return the favor though, I REALLY 
don't want to even think about putting a 12 x 9 .....Nope !

	Reg

    Thanks for all of the info so far people. If anything, I am at the very
    least on my way to get this boat to plane or know why it won't. 
    More info.
    year 1950 (boat and engine)
    Size 22'
    beam 6'
    Hull config. planing type
    engine 6 cylinder flathead
    HP unknown
    Engine capable of delivering 5000 rpm's 
    
    Some background- I bought this boat about 13 years ago with engine and
    cutlass bearing mount removed. After looking at many boats the same
    type I installed the engine with its present angle. I use this boat 
    around Cape Ann for scuba. I have a slip at the Lanctot marina across
    from Popes Landing in Danvers. Again I have been using this boat on
    and off for over 10 years. 
    
    So now you probably want to know why I care now that it does not plane.
    The engine and transmission which is of the planetary gear type,
    both use the same engine oil. When the boat is at rest the engine is at
    some angle. The oil is checked at this angle. Now when I get under way
    the angle increases by a drastic amount and then it should plane out
    giving me close to the same angle I had when at rest. Now because I
    can not get on plane all of the engine oil makes its way to the tranny,
    once it fills to the top it begins blooping out the breather hole on
    top of the tranny. I am sure you all know what happens when you bloop
    oil into the bilge of a boat and mix it with water. It becomes a slimy
    mess and I am kinda tired of cleaning it up.
    
    Lately I have been thinking that possibly my installation was the
    problem. Now in talking to some of you its entirely possible that 
    I do not even have the right prop. So what I am going to do is check
    into it and possibly if have enough space to go with a prop an inch 
    larger in diameter I will take you up on your offer to let me try 
    your prop. 
    
    I will post a note if I straighten this out.
    
    Jerry
    
    Thanks again,
    
    Jerry 
    

    Jerry,  first, even though that engine is able to do 5000 RPM, I'm not
    sure that the old flathead engines were meant to turn that fast.  My
    small block Ford (small pistons, low mass, short stroke) should not be 
    run above 5300 RPM's.  Your engine (either big pistons or long stroke)
    is probably meant to run way below 5000 RPM and you have only been
    lucky that a rod hasn't gone thru the oil pan and out the bottom of
    your boat.  But, since I'm no expert on the 1950 Chrysler Ace engine,
    there is a guy in Tewksbury, Earl Sheehan (Earl's Repair Service,
    508-851-2656) who is considered one if not the expert on old Marine
    engine.  He wouldn't even touch my 25 year old Interceptor motor
    because it was "too modern" and it wouldn't be worth it to me to pay
    him what he charges.  He could either tell you what the max revs should
    be on that engine or direct you to someone who specializes in them. 
    As far as the accuracy of your tach, assuming that it is a mechanical
    drive unit, it could be wearing out after all these years.  You may
    want to convert to a newer electronic tach because of the need to have
    reliable information when it comes to prop selection.
    
    A few things jump out at me from the book.
    1) the distance from the prop to the rudder should be at least 4 inches
    or as required to remove the prop without first removing the rudder
    (something I can't do on my fifteen footer!)
    
    2) the clearance between the bottom of the boat and the prop should be
       2 inches or 10% of the prop diameter, whichever is less.  In your
    current case, that would be 1.2 inches.
    
    3) the normal engine angle should run around 10 - 12 degrees with 16
    degrees being a maximum angle.  Most marine engine builders had a max 
    engine angle recomendation that may not even allow 16 degrees.  In your
    case, you are obviously at too high an angle if oli is coming out of
    the gear.  I wonder if your engine isn't starving for oil when you are
    at such an angle?  I personally think that you should think about both
    going with a larger prop and lowering the angle of the engine if you
    still have room between the bottom of the boat and the propeller.  You
    can buy adjustable prop shaft struts from a number of sources like
    Osco, etc.  You will also probably need to change your shaft log, motor
    mounts and tranny mounts if there is not enough adjustment available.
    This is all starting to get pretty expensive so hopefully the larger
    prop will do it for you.
    
    4) a planing hull boat typically has a speed/length ration of 3.  What
    that means is that the speed that you reach plane should be equal to
    3 times the square route of your WATERLINE LENGTH (not overall length).
    For your boat (assuming a waterline length of say 20') you should reach
    plane at 13.4 knots or 15.4 mph.  You have not mentioned what speed you
    can obtain at wide open throttle.
    
    
     You are welcome to borrow my book although I hesitate to send it thru
    the interoffice mail.  I work in Salem (NIO) and once a week travel to 
    Merrimack.  Are you ever up this way?  Is there anyone out there who
    works in NIO or MK who travels to Shrewsbury?
    
    Wayne

re: 928.17
>>    year 1950 (boat and engine)
>>    Size 22'
>>    beam 6'
>>    Hull config. planing type
>>    engine 6 cylinder flathead
>>    HP unknown
>>    Engine capable of delivering 5000 rpm's 
  
While it does sound like you're under-propped, that is also NOT an easy 
boat to plane.  It's 22' long and only 6' wide!!!?  That thing is like a
knife going through the water.  Assuming an undersized prop, no lifting 
strakes in the wood hull, narrow beam, a 43 year old flathead six, a gross 
weight (displacement) of probably in excess of 3500 pounds including your 
dive gear and passengers, I'd have to say it's a miracle the thing planes
at all under certain conditions.

Since it does plane on "good" days, a switch to the correct prop may allow
you to plane whenever you want.  The other replies were right on the money;
you are over revving the motor at 5000 rpm, and should not run it at that 
speed for more than a few seconds.  4000 rpm is probably a more realistic
limit.  You'll probably want to switch to a prop that will allow you to 
run at the speed you want without doing it at 5000 rpm.  At any rate, if
you continue to run at that rpm, the motor will be destined for the junkyard
in the sky. Especially if all the oil is flowing out of the motor back to 
the gearbox.

As far as the breather goes, the right fix is to prevent the oil from
getting there by correcting the angle problem. Most boats run at a very
steep angle just before they're on plane, so if you can fix the non-planing
problem the overflow from the breather may fix itself.  If not, how about
raising the breather by attaching a hose and running it up higher than the
oil level in the motor.  Kind'a like the 4WD guys do for air intakes in
wet or muddy conditions.

>> I will post a note if I straighten this out.

Hopefully, most of us will still be around to here to read about it by
then.  8^(

Rick

    Alright, some useful information. Thank you so much. Now, assuming the
    info is correct, I can go to my boat and make some quick determinations
    about my installation.
    
    Regarding the revs of my boat, if I ran at 5000 rpm's constant, I would 
    not have an engine. All I meant to accomplish by telling you that is
    the
    fact that the engine has the ability to run at its full capabilities.
    
    Chances are that I will not be able to accomplish what I want, but I
    sure would like to see this antique beauty come up on plane on command.
    
    Thanks again for all of your help.
    
    Jerry

re                       <<< Note 928.20 by JUPITR::CATRON >>>
>                 -< I may just buy the book. It sound helpful >-
    
>    Regarding the revs of my boat, if I ran at 5000 rpm's constant, I would 
>    not have an engine. All I meant to accomplish by telling you that is
>    the
>    fact that the engine has the ability to run at its full capabilities.

	I have been ass_u_me_ing that it can hit 5K when in gear and 
driving the boat....  the above wording sort of suggests that you 
meant it will spin to 5K if you just blip the throttle with the 
transmission in neutral.   Please clarify, will it get to 5K when 
trying to plane the boat ?  If so then I believe in my original 
prognosis (weenie prop).

	Reg

    This is a basic low compression flat head six...I doubt the engine can
    breath well enough to overrev itself (not to mention valve float, which
    can also act as a rev limiter).
    
    By the way, these old sixes are pretty good engines, very smooth, very
    quiet.  
    
    Carl

re: .22
>> This is a basic low compression flat head six...I doubt the engine can
>> breath well enough to overrev itself (not to mention valve float, which
>> can also act as a rev limiter).
   
If the tachometer is to be believed, then the motor is most definitely
breathing well enough to overrev, because 5000 rpm's is too much. Given
the correct prop, gearing, and no cavitation, you're right, the motor
shouldn't overrev.  But with little or no load, almost any motor can be
be made to overrev.

That brings up the question that was mentioned before; how accurate is
the tach?  With a big old marine flathead 6, at 5000 rpm's all kinds of
things should be happening, and none of them good.  One would think that
valve float, the abnormal mechanical noise that the boat operators hears, 
or a connecting rod coming thru the block should prevent the motor from 
running up to 5000 rpm.  Is this the *original* tachometer for this motor?  
If a 4 cylinder tach were substituted, the two extra cylinders would cause 
the tach to read 50% higher than the correct reading.  In this case, a 
reading of 5000 rpm would give a true rpm of 3333rpm, which is MUCH closer
to the range of where the motor should be just as the boat comes up on plane.

So, to the human ear, does the motor *really* sound like it's turning
5000, or do you think it's possible that it's really down around 3300?
Remember, at 5000 rpm, that motor should sound like it's really screaming
and is about to blow.  Do you think it's possible you have a 4 cylinder 
tach?

Rick