88 Ski Supreme Steering Problem

I have a 1988 Ski Supreme. I have checked the fins below, the steering seems to be good and everything on the drive train is tight. I can go about 35-37 mph with no problem but when I get to about 40 or above the boat tries to steer to the left. It is everything I have to hold it from diving hard to the left. If I muscle it and try to steer it to the right the boat tries to nose into the water and it can hardly turn the steering wheel. It is like something else is tryin to turn the boat other than the steering. If I get under about 15mph or stop the boat and let it dive to the left then take off again I have complete steering and control of the boat again. It has happened mostly in rough water. I have taken the the rear seat out and everything looks good! I was out this weekend and noticed it again. If the boat starts to hop going across a wake or some thing it will do it again. I try to steer it back and the boat seems to be nosing over into the water like one of the tracking fins under the boat is turning. I checked it out and the front fin points slightly, I am talking 1/16th of an inch, to the direction it always trys to steer to when the front of the boat bounces out of the water. Can this slight turn in the fin only affect the steering of the boat when the front comes out of the water and grabs water?????? Just a question? I can run at 45mph in smooth water all I want, but if the front end hops out of the water slightly I am screwed..... it starts to turn left. The out drive mount and rudder mount was redone because it had struck something and I noticed the prop is pitched just off center to the left in relation to the prop, but I think this is normal. I know a quick fix, just don't go over 35mph, but I want to barefoot. Please HELP,
Thanks in advance for any help given.

Eric

 

Do you have power steering? The problem could be in the slave cylinder valves. The offset on the shaft is normal to counteract the torque. Also, do you have a trim tab in the rudder? If you do, adjust it towards the side the boat pulls.

 

Late '80's Supreme boats had a problem with cavitation at high speeds in rough water. The problem can be corrected by reworking the prop to slightly different specs. I've been running a reworked prop on my boat since '91 and haven't noticed any negative side effects...I also haven't experienced the cavitation.

I don't have the specs handy, but if you e-mail me at smithmdsmith(at)yahoo.com, I can get them to you.

I will most likely not check this board (nothing personal...just not my thing).