desperate

[b0mbtrack]

Mercuiser, bravo III, MPI. Forgot the model number but is a 2001 boat.
Ran with drive trailered up then had a rhythmic thunk come from drive area. I removed the drive and found I couldn't turn u-joints without using a screwdriver. Rebuilt drive then was able to turn u-joints like they are supposed to be turned. Installed drive and started up engine and found the same thunk, went and replaced the gimbal bearing and tried again but found the same thunk.
Now I am goind crazy, everything in the transom area feels perfectly fine. If it weren't for this thunk i wouldn't think anything at all was wrong. It is a strong enough thunk to shake the engine and it seems more random than timed with the engine. What should i do, i take off the drive and inspect everything but everything turns free and feels fine....

 

[mylesm260]

Re: desperate

Does it do it on the trailer with the ear muffs on?

Can you listen to the drive and try to find the cause that way? Could be the upper gears.

 

[b0mbtrack]

Re: desperate

The drive was rebuilt with all brand new gears and it was shimmed as well. The shaft that the gears ride on and all the shifting and clutch pieces were replaced, just about everything in the drive was changed.

We tried the boat out of the water with the ear muffs on and heard where the noise was coming from with a large screwdriver to our ears. it is pretty much coming from where the gimbal bearing/u-joint area is, but the u-joints were in perfect condition and the gimbal bearing was changed. We very intensely looked in the bellows area for ANYTHING but couldn't find a single thing. Like i said, the u-joints spin nice and free and there is no binding anywhere, if it wasn't for this strange clunk i wouldn't think there was anything wrong.

 

[b0mbtrack]

Re: desperate

UPDATE,
I went ahead and changed the entire u-joint assy and am still having the same problem. I changed all the yokes and crosses, the whole thing. I don't know if i mentioned i changed the gimbal bearing and checked the engine alignment as well.

 

[Alumarine]

Re: desperate

Have you tried running the engine without the drive attached?

 

[b0mbtrack]

Re: desperate

yes, it went nice and smooth. nothing like it does with the drive attached. too bad i don't have another bravo lying around i can throw on there to maybe help diagnose.

 

[mkast]

Re: desperate

Did you align the the engine?

 

[b0mbtrack]

Re: desperate

the engine alignment tool went in nice and easily. i even took an extra u-joint yoke shaft and stuck it in there which went in there nice and easily.

 

[Uraijit]

Re: desperate

By "nice and easy" do you mean that you could move the alignment tool in and out with just a finger and thumb? Did you put grease on the tool, and check the depth of the lines in the grease made by the coupler splines?

The yoke shaft won't tell you anything about alignment.

 

[b0mbtrack]

Re: desperate

i put grease on the actual tool and didn't see any lines that were deeper on one side than the other. its hard to pull it out without hitting the gimbal bearing but i got it a few times without hitting the gimbal bearing.
as far as the yoke shaft, that went in and out nice and easy, i don't think one finger easy though, i thought if anything that would be the best way to tell for alignment (better than the tool) didn't know it wouldn't be good for that, thanks.

 

[achris]

Re: desperate

Sounds like a coupler.... Did you check the alignment every 90 degrees of engine rotation? that what you need to do... ie, 4 times...

Chris.........

 

[b0mbtrack]

Re: desperate

no i didn't even think of trying that, i'll have to give that a shot