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LakePowellDreamin

Help! Drive Shaft Vibration

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LakePowellDreamin

Fellas, help I'm a novice. I've got my family down at the lake. First time this year we have had our 2006 wakesetter VLX out. I'm noticing some vibration during low rpms. I just had the boat tuned up / summerize, not sure if that you has something to do with it. I put the googels on and swam underneath to check the shaft and the prop. No sign of damage and I could easily spin the props by hand. I pulled the middle seat off and put it in gear and noticed the shaft wobbling. I'll post a video. I might be overreacting, but looking for a second opinion.

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GreenMan

If you can actually see the shaft wobbling, you have a seriously bent shaft and it needs to be replaced.

Make sure you aren't seeing an illusion caused by marks or whatever on the shaft that may simply make it appear to be wobbling. An engine misfire may also result in similar vibration symptoms.

Are you certain you have not hit something - the trailer, the ramp, a log, the lake bottom...? It would be difficult to do that sort of damage (a visible deformation to the shaft) without hearing and/or feeling it and knowing something occurred.

You can quite easily check the shaft from either inside or under the boat with this technique. Just hold or tape a bit of wire or a stick or something near the shaft and roll it over by hand to see if the distance from the indicator to the shaft changes. Generally a bent shaft will be a consequence of a propellor strike on a log or similar that will also damage the prop but it is possible that the shaft has somehow hit something on its own without prop damage.

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Edited by GreenMan

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LakePowellDreamin

Thanks for the quick response. I've got a video that I m trying to upload, poor cell service. I got a camera down right by the packing nut, and when in gear that's where I see a wabble. I'm certain we did not hit anything with the prop, while on the lake. Maybe something happened in transit. Anyway to do to test you explained while the boat is on the water?

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justgary

Try again on that video. It's dead.

You can use Greenman's method on the shaft inside the boat just as easily as outside.

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obski

The engine could be misaligned. In either case, the shaft will fail eventually. I know this from experience, unfortunately.

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GreenMan

As Gary said, yes you can use the simple indicator method inside the boat on the water.

That said, if you can actually see the shaft wobbling in the packing gland, the shaft is bent.

I'd suggest that an engine misalignment will not like result in a shaft wobble but a permanent 'curve' or bow in the shaft that stresses the shaft with each rotation until it work hardens itself to failure. In that case, you aren't likely to see any evidence of it without undoing the coupling and making some other measurements.

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justgary

It depends on the rotation rate. At some point, the shaft curve can couple with the rotation and cause interesting effects.

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Dare2goBare

Hey GreenMan, where did you pick up that Flux alignment capacitor stabilizer indicator??

Man some days I just can't help myself....Sorry.....lol..lol.....:Doh:

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GreenMan

It depends on the rotation rate. At some point, the shaft curve can couple with the rotation and cause interesting effects.

Yes, true.

Probs not at idle speed with a thing as stiff as a drive shaft?

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GreenMan

Hey GreenMan, where did you pick up that Flux alignment capacitor stabilizer indicator??

Man some days I just can't help myself....Sorry.....lol..lol..... :Doh:

Ha, Dare!

It works well as an adjunct to a late model electronic vectorial runout compensator. :)

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LakePowellDreamin

I got the video to load. Take a look at the wobble. What you think?

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LakePowellDreamin
prop test

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Sixball

All coupling bolts tight should have 4 of them. Its not unheard of them coming lose.

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LakePowellDreamin

coupling bolts.from the beginning it seemed like something was just loose. That seems like it makes the most sense to me. I don't believe the shaft is bent, where would I find the coupling bolts? Are they above or below the packing nut?

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LakePowellDreamin

I think I got it. I believe I'm missing 2 coupling bolts. Take a look, is that right

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justgary

You also need to change the coupler. Pause at 11 seconds and you can see the crack.

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DocPhil

You also need to change the coupler. Pause at 11 seconds and you can see the crack.

good eye.

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LakePowellDreamin

@justgary you're right, Great catch! Sure enough, that coupler piece is cracked all the way through. Is that easy to replace? We've got another weekend trip in two weeks. Do I put the 2 missing bolts in and limp along till the end of the season or get it fixed right away?

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Bozboat

Personally, I would not be able to sleep until I fixed it.

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GreenMan

YIKES! That is seriously wobbling! As Gary said, the coupler is apparently cracked. Do not use the boat until you replace it and fit four bolts. It is probably cracked due to use with two adjacent bolts missing.

If the coupler breaks off under load and speed, the wayward parts and flailing shaft end could do all sorts of further damage.

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LakePowellDreamin

Thanks guys, I'm trying to order the coupler online, does anyone know the model part number? Also, how difficult of repair is this? Is it as simple as pulling the old one off and putting the new one on? Does the engine need to come out in order to get to it?

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