inborad to outboard

[boating dave]

Hello,
what I am having a proublem with is my 1980 chris craft, there was a single engine inboard at one time and someone changed it to a in/out board. what I am having a hard time with is that when I get it up on plane it rolls side to side and will not stay flat over 20 knots. I was told that is has to do with the shape of the hull, because it was designed for an inboard. what I am doing is trying to find out a little info about it and maybe try to play with the bottom a little. I can build just about anything but have no ideal about hulls. If anyone has any advise I would really apreciate it. thanks
Dave

[Sean Herron]

Hello...

Try some movable weight forward - a water tank - or other....

Also Bennett tabs...


SH.

[boating dave]

I have trim tabs on the boat, it does push the front of the boat down. However is still tips at high speed or at 20 mph anyhow. what I was told is that the boat hull was designed for a inboard which pulls the boat in the water as it goes, with a outboard it pushes the boat out of the water and alows to much of the boat to come out of the water making it top heavy. I am not sure put that does make sence. Either way I would like to know if there is anything I could do to help.
thanks
Dave

[JR-Shine]

trim tabs - should be all you need

[Richard Petersen]

I read age of boat as 1930 and went after typical rot as reason for stern drive conversion. 1980 boats were already glass. Not important. Old style shaft drives had all the propthrust pushing foward and most importantly UP at a thrust bearing just behind trans coupling. That pressure point lifts the entire boat a little more evenly than the stern drive ever can. Putting in bigger engines usually only cause a faster but not a WEIRDER running boat. Torque steering- right and left pull become more noticable.The present boat now has a new and bad balance point that moves back and forth with speed. Do not AIR IT OUT in choppy or stormy waves while doing a turn. It is not a CHRIS CRAFT any more. Please be carefull. Naval designers, correct me if I am over doing my concern for him. Rich.