Higher speed wobble

I recently purchased a 1994 Correct craft Sport Nautique with a 351. When the boat reaches about 34 mph it begins to rock and feel like it’s twisting to the right. Very unstable. It feels like it’s getting on plane plane but very wobbly. Around 40+ The boat gets very unstable. I’m trying to figure out the cause. My thought is it may be a bent shaft or prop. Yes either or it’s not very noticeable. The prop does have some damage but appears slight. Any thoughts or suggestions?

The tolerance on a shaft is 0.003” of runout. You won’t be able to see that, you would have to measure it. If you are seeing damage to the prop that is bad from the imbalance it causes as well as it could indicate damage to the rest of the running gear. Sounds like it is new to you so I would recommend checking shaft straightness and having your prop repaired. Probably should check alignment as well. Don’t know that it is the cause of twisting to the right at 34, but prop damage is a red flag.

Question on preload...which way should the tunable part of the rudder point towards for the preload? Does it depend on the prop rotation?

David,

I kinda figure that since they put an adjustable rudder on his new boat, they must have put something about adjusting it in the owners manual

Correct in the left hand prop and thanks for the link. I have my hard copy manual and that looks just like it. Some info but mainly trial and error unless your boat is pulling to one side already. Mine is currently set dead straight which begged my question if it should correlate with prop rotation. I’ll go with Larry’s thoughts for my first change. I really don’t have an issue at speed but plan to offset slightly like my old boat was. This boat does not like to drive straight at idle which I’m hoping to be fixed with this adjustment too. Not sure it will.

Original poster, sorry for the hijack. Back to your question. I agree that shaft runout and prop would probably create vibration and not your issue. I like the suggestions of checking rudder first. We had some issues with our ski tique acting squirrelly coming off the throttle and we had a loose rudder. Drove great otherwise. Also tracking fin and hull work could be issues.

Nautique is turning out boats with LH props? like Malibu has always done? How do they do that, reduction trans into VDrive with standard rotation engine?

It would appear, based on reading Ken's link, that I, and those of you that said what I said makes sense, were incorrect, despite the sound logic. Doesnt make sense to me, but what do I know.

Just seems counter intuitive Tim.  Guidance says if boat is pulling to the left, you rotate the tab to the left.  I would think you would rotate it to the right to offset the pull to the left.  But like I said, what do I know.

8122pbrainard wrote: Yes, I thought the manual instructions were very vague since they didn't mention anything about prop rotation causing a pull to ether direction.

75 Tique wrote: Just seems counter intuitive Tim.  Guidance says if boat is pulling to the left, you rotate the tab to the left.  I would think you would rotate it to the right to offset the pull to the left.  But like I said, what do I know.

75 Tique wrote:   I assumed it was comparable to airplane dynamics and I have been told you know something about airplanes so I trust your interpretation.

 

75 Tique wrote:   I assumed it was comparable to airplane dynamics and I have been told you know something about airplanes so I trust your interpretation.