Prop/shaft issue...terrible vibration - 84 Supra Rider

[chautauquasun]

84 Supra Rider
PCM 351w
1:1 velvet drive.

So we were out today and now have two new issues. Figures....boat has run fantastic for the last 7 years...I spend money to put in a new interior and it has been summer of issues.

So the first issue, We were out this morning skiing, wake boarding and skiing Toward the end of the morning we started to get a very bad vibration. Came back to the dock and I discovered that some how we picked up a pretty large shot of yellow nylon rope from the water. It was wound in tight. I cut it out and then started looking at the prop. Its been a long time since I replaced it and am not sure how much room there should be between the prop and prop shaft mount. The prop seems to be loose now as well. I am thinking that maybe the tightly wound rope moved the prop down the shaft because I took it back out and had a bad vibration and almost seemed like maybe the prop was loose and spinning on the shaft. Not sure about that but did seem that when I gave it power that the engine revved faster than normal and had no power.

Anyone know how much space should be between the prop and prop shat mount?

thanks
Dan

[CJD]

Mine has about a finger's space to the strut. If you at all suspect a loose prop, I wouldn't run it at all until you have a chance to put a wrench on it and check. I do doubt that the prop is spinning, as that is not a matter of spinning a little. If it spins you will immediately lose all drive.

Take a good look at the strut cutlass bearing too. The rope may have damaged that, allowing the shaft some play to vibrate. If all that checks good, then you may have bent the prop.

[chautauquasun]

To check the cutlass bearing I think I need to pull the shaft correct? I tried to loosen the shaft to see about moving it or removing it but it didn't seem to want to move at all. There doesn't seem to be much play in the shaft. I took the boat out today. You don't notice any vibration at idle speeds but get a bad vibration around 20 mph that goes away as you add speed. Could this just be the prop? I noticed dings in it yesterday and tried to straighten them out. Could that have thown it out of balance. What I did to it certainly looked a lot better than what it did. not sure what to do. Should I remove the prop and see about getting it refurbished first...then go further. I definitely have about an inch and quarter or inch and a half between the strut and the prop. I just cant remember is this is how it was. I tried to loosen the prop shaft and push it/hit it up towards the boat but it didn't move a all. I didn't want to be too aggressive with it and damage the shaft.

any thoughts?

[CJD]

Yes...prop first. Any slight difference in pitch between the blades will cause vibration. A prop shop will straighten it up and smooth it out. If all else feels solid you should be good. Make sure the shaft is not nicked or scratched badly when reinstalling the prop. If no melting or looseness at the cutlass bearing it should be good to.