Boat is Swaying bad at high speed
 

We just got our boat back in the water today, it is a 1986 34' Scarab III. We just dropped new engines in, approx. 500hp, and put new TRS drives on with bullet nose cones. We also replaced the gimble housings. Right now we are using our old props 3 blade Mirage 23 pitch at 15.25 diameter. Last year the boat ran straight with no sway. Now when you you get it up past 50mph, the stern walks back and forth enough to scare you. Does anybody have any ideas what this could be caused by. Thanks.

Re: Boat is Swaying bad at high speed
 

It could be the nose cone. as long as everything is tight and nothing else changed this could be it. Are you turning in or out? In can give stern lift that feels funny, Rambunctious did this and it scared him. He turned out and switched to in, this made the boat squirrelly. You can try this also, just remember when the sticks are forward you will be in reverse. Did it have tyranny's before? If not you moved things forward and took away some stern weight. I would try the rotation first.

Re: Boat is Swaying bad at high speed
 

How tight is your steering? Nose cones will amplify chinewalk on a boat that has loose cable steering,mine did! Hydraulic steering took alot of it away,Smitty

Re: Boat is Swaying bad at high speed
 

Houston Prop did some work on my prop that cleaned up my chine walk. New motors, more torque could be causing the chine walk.

Re: Boat is Swaying bad at high speed
 

Go to a 4 blade

Re: Boat is Swaying bad at high speed
 

What about toe-in/toe-out? Have you checked that's at least neutral? Measure front and back edges of the drives, and they should be the same. You'll find 20 opinions on how much to toe in or out depending on in or out rotation, but neutral is a good starting point. Is there any side-to-side slop in the the drives? Do you have a tie bar?

My Fountain's a$$ danced around when I first got it. It had TRS's with nose cones. At 75mph+ it has a puckering effect. After going to a Latham full hydraulic steering setup, she goes like a rail up through 80. I rotate outward, and set toe at neutral.

Good luck,
Brian

Re: Boat is Swaying bad at high speed
 

As I added more power to my scarab the bow would getting increasing lowing in the water. I attributed this to the hook in the hull and the fact I was going faster than the original intent. Switching prop rotation to spinning in pulled the stern lower and the water and improved drivabiliy significant.

Word of caution though, most trs tranny clutch packs are directional and cannot take being run in reverse (as you can a bravo in reverse). I would switch drives to be safe for testing.

BT :cool:

Re: Boat is Swaying bad at high speed
 

BT, beat me to it, you cant just swap props cause unlike bravo's, trs can't run under heavy load in reverse. Trannys can't handle it.