Bad vibration

[bradcraig78]

3rd time out this season and was driving when all of a sudden the boat bogged down and started vibrating. I took it back to my boat lift to check the prop. There are a few nicks but nothing too noticeable.

Question is if I take the prop off and lower it back in water to test if the vibration still exisit and if the vibration has stopped will this accurately diagnose the problem?

Or would a shaft alignment only vibrate if prop is on?

[usaski1]

That should do it... If you place it in gear with the prop off the boat, if you still get the bad vibes, its shaft or coupling issues. I'd certainly try it. I'm fighting my own bad vibes too, I need to try my own advice.

[maxpower220]

It could be the prop, the strut bushings, a bend shaft, or perhaps a misalignment.

In your case, you should try to determine why the boat "bogged down". Did the engine ever stop bogging? I am assuming that there is no vibration when the engine is running but no in gear.

[bradcraig78]

not sure why it bogged down. Felt almost like hitting a sand bar but I was in 30 ft of water and I know there was no sand bar in that area of the lake. I don't remember any large thumps like I would if I hit something. When the engine is in neutral you can rev it up without any vibrations.

[usaski1]

If you are describing something very abrupt, and did not hit something.. You can still move when in gear right? So its not a snapped shaft. Something that abrupt concerns me though... I have vibration issues, but its not abrupt...

[bradcraig78]

No the shaft didn't snap but i could only go about 5 mph back to the dock, anything above that causes a bad vibration and didn't want to take any chances.

[kaneboats]

Sounds to me like you bent the shaft. Look the prop over more carefully. You can remove the prop and run the boat- put it in gear on the trailer and watch the shaft-- you'll know immediately if it is bent.

[bradcraig78]

I put the boat in gear while on the boat lift. I ran it for about 30 seconds in gear and no vibration. Does this mean that it's the prop? I looked at the vdrive while in gear at the point where you would adjust the alignment under the transmission and didn't notice any wobbling. I haven't taken the prop off yet (waiting on friends prop puller) but when I look at it it only looks like a few nicks on one blade. Would a bent shaft or allignment issue vibrate out of water? Thanks for all the replays

[Hoopskier]

I really dont have much input here, but one observation is that when you remove your propeller; you are removing all the load from the engine/drivetrain. Few things I would check/try (some of them have already been mentioned

1. visual inspection both inside and out.
2. Does the propeller turn by hand? There should be some drag but still turnable, at least mine is that way.
3. Does the engine run well. Using the gear bypass button, can the engine rev up w/o being in gear?
4. When idleing in gear (on the lift) make sure you look u under the boat.

When runnign out of the water, or no propeller, there is no load on the strut bushing or coupler. Hope you get it figured out.

[DOCDRS]

After 10 years on my 99 my prop had no marks on it at all. After 3 years on my 09 no marks on my prop. If your prop had no marks on it and now it does then you hit something. Check your alignment with a feeler gauge at the coupler and if its good then its your prop. Not rocket science.

[usaski1]

Not to thread jack, but all my vibes are at 650-800 rpm... after that, no more bad vibes... If I was out of allignment, I'd have bad vibes everywhere, right?

how are you running it in gear, on the trailer, and seeing the prop? You got water hooked up to it?

[DOCDRS]

Why is it that everyone does not want to check their alignment?. Its easy and its a cheap and easy fix if its out. Do the simple stuff first, then go to the prop. Things settle and wear and alignment is a yearly maintenance item.

[kaneboats]

FYI, you may not be able to see an issue with the prop. I got one back from the shop last year that was not done right. Threw me for a loop for a couple of days before I figured out that the prop was not right. Sent it back to them and they got it right. A strike to a sand bar may not show up much to the naked eye buy if the prop is out you can sure feel it even if you can't see it. Check your alignment though.

Edit: Also check your shaft coupler bolts. If you get that far you are half way to checking the alignment anyway. Those bolts have nylock nuts but can vibrate loose. Everybody should check them twice a season or so. I got the boat back from the dealership one time with all the nuts not tightened up.

[DOCDRS]

FYI, you may not be able to see an issue with the prop. I got one back from the shop last year that was not done right. Threw me for a loop for a couple of days before I figured out that the prop was not right. Sent it back to them and they got it right. A strike to a sand bar may not show up much to the naked eye buy if the prop is out you can sure feel it even if you can't see it. Check your alignment though.

Edit: Also check your shaft coupler bolts. If you get that far you are half way to checking the alignment anyway. Those bolts have nylock nuts but can vibrate loose. Everybody should check them twice a season or so. I got the boat back from the dealership one time with all the nuts not tightened up.

Also as a note , after a while the nylon in the nylock bolts can become ineffective and they should be replaced after they have been adjusted 6-8 times.

[kaneboats]

Good stuff, Doc. Follow Doc's advice and take good care of your nuts.

[DOCDRS]

And when my wife asks me if I'm listening , I tell her I'm trying to free up some space in my head from all the useful little tidbits of info that somehow has cluttered up my brain......i guess I really need a brain rinse...:)

[jpetty3023]

He said nuts....hehe


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[KG's Supra24]

I'm betting prop.

You aren't overlooking something obvious right? I had the bad vibration issue once. Not 1 of the 3 blades had a knick, however the whole 4th blade was gone. :o

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[bradcraig78]

Update. So I checked the alignment which looked good and decided to put the boat on trailor to change prop/shaft etc.. As I'm idling out of cove I don't feel any vibration so as I leave the cove I speed up and the vibration is gone. Boat runs as usual. Thinking maybe I ran over some weeds a rope which must have come loose before putting it on the lift. The one thing I didn't do was turn the engine off after vibration started. I just put it in neutral then idled back to dock. Any thoughts?

[kaneboats]

One thought: You're darn lucky!

[DOCDRS]

Definitely could have been something wrapped around the prop. Look closely around the strut ( for and aft) to make sure there isn't any fishing line wrapped around the shaft.