Bravo II knock and flattened shaft o-rings

[fishaman]

Hi, I wonder if it is a known problem.

An irregular knock is coming from the gimbal area at idle. Also, when I remove the outdrive, the gimbal o-rings on the shaft are completely flattened, they are half-moon in cross section, as if all the rubber outside the groove had been shaved off.
I had found similar symptoms in only one thread (http://forums.iboats.com/showthread.php?t=472738), and there the fix was to change the out-of-center coupler. However, when I check my alignment with the bar, it looks good, spline marks are long and uniform all around.

Mine is an old style Bravo II yoke shaft without the groove for a coupler o-ring, and there's close to 1000 hours on this shaft. The splines look good, zero corrosion, the bellows never leaked, but there may be some wear. I have not yet tried to disconnect it, and see how much play it has when inserted in the coupler. The aluminum coupler has only about 200 hours on it, came with allegedly 50 hour engine I have installed two years ago.

Should I:

- replace the shaft (about $100, easy work)
or
- replace the coupler (between 300 and 600, plus engine removal work)
or
- replace both
or
- do nothing, since it runs well at high RPM, and they all clank a little at idle ?

Any shared previous experience with the similar symptoms will be greatly appreciated.

 

[Don S]

Re: Bravo II knock and flattened shaft o-rings

An irregular knock is coming from the gimbal area at idle. Also, when I remove the outdrive, the gimbal o-rings on the shaft are completely flattened, they are half-moon in cross section, as if all the rubber outside the groove had been shaved off.

They are just flattened from being inside the gimbal bearing. Do they get replaced when you remove the drive for yearly service?

If the gimbal bearing is perfectly smooth, no reason to replace it. You may have worn ujoints. May not feel a problem when moving by hand, but they can cause a noise when the get grooves worn in them. They can be replaced without replacing the yokes.
Do you get any difference in noises when turning or trimming while moving.

Bravo drives can rattle the upper gears a little bit in neutral, especially if the engine has a miss in it.

 

[fishaman]

Re: Bravo II knock and flattened shaft o-rings

Thanks Don, I think you have pointed to the root of the problem: my engine idles differently after dewinterizing this year, needs a tuneup, so probably it made irregular clanking more pronounced. Otherwise, everything is fairly new, gimbal bearing, ujoints, etc. replaced two years ago. Gimbal bearing is smooth and has a lot of grease.

I saw the flattened o-rings (the red type) when I removed the outdrive last month after two years. They were replaced with the black ones from a new Bravo seal kit at the same time.

I will check if the sound changes when the drive is turned, and report.