Conference vicki::boats

    Hi Rich
    
    How many props does your friend burn up during the course of a year? Is
    he really a friend?
    
    What happens when the prop gets air into it is it Cavitates. This does
    a few things.
    
    1) Burns the metal rightoff the blades causing nasty holes and things.
    
    2) Throws the prop and hence the driveshaft of the engine  outof
    balance. The bearings soon fall apart and then reallybad things happen!
    
    3) the boat usually has a loss of control at high speed.
    
    4) But don't worry, because  the boat  will fall off plane as the engine
    overrevs and blows metal parts like pistons,rods ect out of its
    cylinders.
    
    In short its not a good move.
    
    The Cavitation plate should be level to +/- 1 inch of the keel.for
    maximum proformance.
    
    Boat designers  relize that they have constraints as to engine
    placement when they build the boat. Don't Muck with it!
    
                                    :>)   Walt
    

    	While I agree with Walt that problems can arise by raising the
    motor too much, some performance improvement is realized by doing it 
    within certain limits. Bass boats for example frequently do it to get
    more performance.
    	Merc puts out a pamphlet called "High Performance Boating", or 
    something like that. It goes into the positive and negative aspects of 
    raising the motor. I'll try to look it up at home tonight. 
    	I remember the pamphlet discussing a chopper prop which is 
    designed to brake the surface of the water while its operating. 
    	The main concern with higher mounting is making sure that the motor 
    still gets enough water to keep cool and doesn't cavitate
        After reading the pamphlet, I concluded that the risks outweighed
    the benefits for normal fishing or cruising applications.
    Regards,
    Paul 
        

    Thanks for the responses.  The information one can access through Notes
    amazes me.  Both responses where helpful.
    
    Thanks again,
    Rich

    Rich,
    	I was out of town Friday and I forgot to look up that pamphlet.
    I'll try tonight.
    Paul

    	Well I finally found the pamphlet that mentions raising the engine.
    It was in the Merc pamphlet on props. I don't have it in front of me
    right now so I'm quoting from memory...a very risky business in my case
    :^)
    	Anyway It stated that for normal operation the anti cav plate
    should be in line with the lowest part of the hull. Increasing the
    height up to 3 inches above that provides some improvement in
    performance and handling due to drag reduction etc. I guess improvement
    continues with increased height until the point that cavitation occurs.
    As I said in an earlier reply, there are props designed to break the
    water's surface during operation.
    	Regarding risk, it was mentioned that operating at increased height
    does pose significant risks due to the fact that insufficient water may
    be sucked in for proper cooling. It also inserted a statement to the
    effect that operating this way voids your warrantee.
    	I got the impression that it was a means of squeezing out more
    performance but it is best suited for short haul racing rather than
     "average" recreational boating.
    Regards,
    Paul

    Thanks Paul for your add insight.  I appreciate the time you spent
    reviewing the pamphlet.
    
    Thanks again,
    Richf