Volvo SX Vibration

[stvptguy]

So I was on the water tonight and hit something underwater going at a very slow speed. I believe it might have been a underwater floating log on the river. I immediately turned off engine, inspected things and all appeared to be the same as it was before.

When I started the engine, all was fine. As soon as I put into gear, I could feel a vibration throughout the boat. Vibration would get much worst over 1200 RPMs when moving. Engine ran fine in neutral, as well as out of gear at higher RPM's.

When I got the boat out of the water, the prop and lower fin did not look any more damaged than it did before. The boat had previously needed a prop replacement from the prior owner from hitting a stump. I did notice that the larger prop nut (from what I can tell on my diagrams that's the one) was finger tight only.

So, my question is do people thing that I just need to retighten things down and try again, or is there something else wrong? I have a spare prop in the garage I can put on if just the little (and they are little) dings on the prop fins could cause that much vibration.

The engine is a 2003 Volvo Penta 5.0 GL-C w/ SX outdrive.

Thanks

 

[CharlieB]

Re: Volvo SX Vibration

Try the other prop, you would be surprised at how much even 'little' dings have a 'big' bite on the water. Especially as the 'bite' increases exponentially as RPM increases.

 

[Bondo]

Re: Volvo SX Vibration

Ayuh,.....

Check to see if the Propshaft got Bent......

 

[stvptguy]

Re: Volvo SX Vibration

After I tightened the nuts and prop up, I started on the trailer with motor muffs, and no vibration when put into gear. I then took out to the lake and felt the same vibration at 1000 rpm.

I took the boat into the dealer, and they only got a brief look at the prop and the lower unit. They did not thing anything with a prop, or even the spin of the prop would cause it as it all appeared to look ok.

I am questioning if I actually hit anything now. Is there anything that would possibly happen with a U Joint or Gimbal that could have felt/sounded like a "thud", and then cause the vibrations? They were saying that somelike like that could be wrong, but I want to make sure they are not just taking me for a ride.

Any thoughts?

 

[Don S]

Re: Volvo SX Vibration

Is there anything that would possibly happen with a U Joint or Gimbal that could have felt/sounded like a "thud", and then cause the vibrations?

Pull the drive and check them. Any roughness in the gimbal bearing or the ujoints could cause a vibration. Along with a bent prop shaft or damaged prop.
Did they check the prop shaft to see if it was bent? No way can they just look at it and be able to tell.

 

[KJSmitty]

Re: Volvo SX Vibration

Try the other prop, you would be surprised at how much even 'little' dings have a 'big' bite on the water. Especially as the 'bite' increases exponentially as RPM increases.

I can attest to the above, could not see the small smooth "tweak" in my prop but it sure made a ruckus. That's the problem with many TX lakes, many a tree under there...

If you have another prop (mentioned you did) or possibly could borrow one that would be the first item I would try to rule out. That and use a dial indicator on the prop shaft to check for trueness. I do not know the tolerance for yours but my DP was ~.002 or .003 inch (not much to say the least).

A "slightly" bent prop or shaft wouldn't vibrate out of the water-engine run on muffs etc neeeaar like it "could" while churning water.


Good luck

 

[stvptguy]

Re: Volvo SX Vibration

Well, I feel like an idiot, but at least the problem is solved and I can get back on the water. It was the prop. After looking at the prop 10+ times after the problem started, I didn't see that one of the fins on the prop wasn't really damaged like a piece broke off, etc; it was that the fin's angle was adjusted when I hit the object. I should have saw that!

Replaced the prop (had to buy a new one) and it is working fine. Of course, the dealer made money since I had them do it when I could have done that simple fix.

Thanks for everyone's comments, and glad it was a fairly "cheap" fix.

 

[Don S]

Re: Volvo SX Vibration

There are prop shops that repair props all over the country. Might send your damaged prop out for repairs so you have a spare handy.