Transmissions vibration?

Up date , after removing the prop a crack was clearly visible in the drive shaft. I’m lucky I didn’t lose my prop. Long story short , I have a new drive shaft new strut bushings,strut is checked out and prop checked and true. I think the shaft cracked after being straightened before. I lapped the coupler and prop to the new shaft and realigned engine to the new shaft and boat is running smooth. Never felt a strike but maybe shaft just cracked over time. Thanks to all on ideas and commentary.

Gski wrote: Yes it’s running a left hand prop. I’m getting the old shaft straightened and he’s also making a duplicate. They are already double taper shafts. The best part is my ski buddy does a lot of business with the guy making and straightening so I’m getting a real good deal. Also I’ll get a new strut bushing , I’ll install and test it out. This stuff I’ve been through before. It’s just hard to believe we didn’t feel when it got bent

Yes it’s running a left hand prop. I’m getting the old shaft straightened and he’s also making a duplicate. They are already double taper shafts. The best part is my ski buddy does a lot of business with the guy making and straightening so I’m getting a real good deal. Also I’ll get a new strut bushing , I’ll install and test it out. This stuff I’ve been through before. It’s just hard to believe we didn’t feel when it got bent

Gski wrote: We’ll call me stupid ! I was fortunate enough for a marine mechanic to stop by and he found the problem quickly. The prop shaft is bent . I’d turned it a number of times and thought I had a good few. Guess I’m cross eyed. Thanks to all for your thought and ideas I’ll post after I get repairs done.

The boat is 30 years old but it had 118 hours when I got it. I’m not upset about it having problems , I just need to figure out what’s wrong and how to fix it.  Winters coming and I hope to ski a bit more😎

Vibration is more pronounced forward but that may be due to not using that much rpm in reverse. My question is would slippage seem more like a vibration especially as at 34 mph as aposed to 1200-1500 rpm in reverse. We’re pretty sure shaft and prop are good but I could put my spare on when I get it home. With the engine off I can turn the prop smoothly by hand, thinking it may not be bearings or such. By the way it’s a 91 ski brendella with pcm 351 and pcm 40a. It’s got 850 hours most all pulling skiers at 34 mph, I’ve had for 25 years.

Glen,

I’ve checked the motor and it’s running smoothly. I’ve also looked at the coupler it seems to be in good shape. If it is the damper plate would that create slippage and some added heat to the transmission?

Glen,

No "pressure plate" on a boat. Instead there's a damper plate bolted to the flywheel that connects the trans. From your description, I'd say it's going bad.