Heavy vibration on 1996 SN

[Searay]

I was leaving the lake a few weeks ago and struck something hard below the surface of the water. Afterward I had a bad vibration so I inspected the prop and found 2 of the 4 blades were bent. I straightened them the best I could by hand using a hammer like I ha in the past hoping it was good enough. (I also notice that prop turned hard - I needed 2 hands) Well, this time I didn't get so lucky. So I removed the prop and replaced it with the spare used 3 blade that came with my boat that didn't look too bad and headed out. No luck again as the vibration is still bad. I also noticed that I was now getting a ton of water in the bilge. After 5 minutes of ski speed running, I was pumping out a couple of gallons. When I got home I indicated the shaft near the prop and found that it was OOR about .024". I then checked it between the strut and where it enters the boat and got .008". Can someone tell me what the tolerances are for shaft straightness? If this is out of spec, can it be straightened or is it better to buy a new one? What else do I need to do and what will be the approximate cost of repair. Thanks....

[WakeSlayer]

RE: Heavy vibration on 1996 SN

You can try to have a shop straighten it, but my opinion is to replace it. You must have hit that really hard.
Is the water from the shaft packing? Wonder if you banged your rudder too. I would set it in the water and look to see where it is coming from. You also need to check your strut. Maybe you broke that a little loose and are taking water through the bolts? Struts can be straightened. Make sure if you remove it you clean up the area and reseal with 3M 5200. Obviously, after you get all this sorted, you need to do a good alignment.

[DanielC]

RE: Heavy vibration on 1996 SN

Max shaft runout, .003
When my boat is warm, the prop shaft turns freely, and evenly. I can carefully "flip the prop" by one blade, and it will turn about 1 1/2 to two more revolutions.
You might of also bent the propshaft strut. Check the shaft alignment after you get a straight propshaft, one way or another.

[WakeSlayer]

RE: Heavy vibration on 1996 SN

I thought I recalled .002 as the max tolerance, but was uncertain so did not post the number. I am going to say either Daniel's number or mine are right. Anything more than that and you start to chance trans problems sooner than later, and will get vibration.

[DanielC]

RE: Heavy vibration on 1996 SN

Ideally, you want zero. .003 is acceptable, and may be a little buzzy, or it might run smooth. Very few props are perfect, and if you get a prop that cancels out a very shaft bend, it might run smooth. Put another prop on the same shaft, and it might vibrate.

[2gofaster]

RE: Heavy vibration on 1996 SN

Time to pull everything apart and have the shaft checked. It's possible that the strut has moved or is bent and that's where the runout comes from. Or the shaft could be bent. Or both.

[Searay]

Thanks guys. The water looks to be coming through the packing. The closest Nautique dealer to me is about 2 and half hours away. I don't think any of the local shops here in NE PA have too much experience with inboards. Is it a big job, and what is the proper procedure for removing the shaft to have it checked? I have insurance so at least most of my expense should be covered. The worst part is we are probably done skiing for this year.

[SNobsessed]

Searay - If you search for 'Shaft Removal' ,'Alignment', & 'Strut Removal' on CorrectCraftFan.com, you will get plenty of info on how to do this yourself. I recommend a double taper shaft (ARE from SkiDim) as that is the easiest to maintain long term. You can just saw the old one out & not bother with removal of the coupling (worst part of the job). Use GoreTex packing when you put it back together. You might also want to replace the strut bushings if you have more than a couple hundred hours on it.

This is really worth spending the time to get it right. I would bet that you will do a better job than a marina because it is your boat & you will go the extra mile to get the alignment precise.