Conference vicki::boats

    The general idea with any type of planning hull is to get her on plane
    as quickly as possible. This minimises engine strain and conserves
    fuel. To utilize the trim feature- Upon starting, trim prop inwards or
    down fully. This will force the bow downward and the stern up. Nail the 
    throttle until boat climbs on plane. Then back down the throttle until
    equilibrium is obtained. next- slowly increase trim angle and observe
    RPM's increase. if you trim too much the boat will fall off plane,
    loose speed and RPM,s.
    
    With practice you will be able to adjust the trim simitanously to
    acceleration and compensate for variable loads and sea/weather
    conditions to obtain the optimum performance desired.
    
    Then you can research propeller design for even more control.
    
                              Sea Ya Later
    
                               Walt
    

    It's been a long time since anyone replied to this note, but here goes.
    
    I have a 15' aliminum Sea Nymph with 70 horse evinrude with power tilt.
    I see that the boat almost leaps out of the water with the motor
    tilted all the way down, while it takes a bit longer with the tilt up
    to, lets say, level on the tilt guage. 
    
    My problem is that I perceive little if any change in speed by tilting
    the motor up after coming to plane. I do notice that I lose a good deal
    of steering control with the motor in the upper range. This I suppose
    can be attributed to less keel in the water, or only the back of the
    boat.
    
    If I trim the motor up far enough, I hear alot of noise that I think
    might be cavitation? Also the boat gets a bit twitchy. 
    
    Could it just be a case of the boat being sufficiently powered as to 
    make the top end advantage of power tilt negligible?
    
    Please let me know what you think!
    
    Thanks!

    also, I don't have a tach or speedo.
    
    The boat is wicked fast in the top end, so I'm not complaining, just
    wondering if I'm missing something.

    
    the way i use my trim is 
    take off all the way down this gives me best out of the hole pull.
    when i reach a plane i start to trim out this will give me up to
    5 mph more and takes strain off the motor.
    there is a point where trimming up only throws water up (wasting
    thrust) and can make the boat wander and chime walk badly.
    
    another trick if your trying to pull out skiers and cant get your revs
    up because of a high pitch prop or small motor,
    is to trim up allowing cavitation so the revs come up then slowly
    trim down,this can be risky in high power lightweight boats as 
    the prop can bite pushing the back down front up and flip backwards.
       
    if your trying to gain speed you could try raising the motor an inch 
    or two (watch your water pressure for cooling)
    
    thats basically how i run mine however im running a merc mod vp 225+ hp
    on a 17 foot runabout with the motor 6 and a half inches raised
    and a 26 pitch chopper propeller but im set up for ski racing.
    
    your hull may be so light your just lifting straight out and theres
    not enough hull in the water for trimming to make a big difference.
    however if you were to run a speedo and a tacho i think youd see
    some changes as you trim.
    
    hope this is of some help
    
    the other reg
    

    Re .2>
    	I don't know if I can answer your base question but what do I
    think? I think a 70 hp on a 15' Aluminum boat is a package that won't
    perform well at a high tilt angle so don't expect it to. Also I think 
    you could pick an angle and leave it there unless you change the load,
    i.e when towing a skier. You should have no problem getting up on
    plane and therefore don't even have to worry about playing with the 
    trim angle at all.
    	For normal operation I'd trim for such things as comfortable steering 
    (both to port and starboard) and minimal spray from the prop. When
    these conditions are met you have assumed the proper attitude. 
         

    Thanks for the quick replies!
    
    I guess the tilt will not prove to be all that critical in my case, but
    I'm glad I got it anyway, as my lake is quite shallow in places.
    
    Thanks!

I recently purchased a '88 Searay 270 w/twin (260hp) mercruiser stern
drives.  It also has trim tabs.

My question is to other owners/operators with the same kind of set up:

How do you trim your boat?  My previous single stern drive boat was
easy:  Full throttle, pull it back when you get on plane, trim the
stern drive for maximum speed, throttle back some more (or not :-).

My new boat, I'm not so sure.  Tabs bow-down, sterndrives full down to
start seems obvious enough.  Then what.  I suppose tabs to
neutral-position might be next.  Then sterndrives?  The previous owner
just "tapped" the sterndrive button up a little (i.e. don't play with
the sterndrive elevation much).  But in my runs this w/e, I could get
alot more speed with the drives substantially up - just like my
previous stern drive.  For the sake of discussion, I propose the
following assumptions: smooth water, boat balanced port to starboard,
goal is maximum speed, load is minimal - two people.

What do you do?

ptc