OMC - Vibration, u-joints? gimbal bearing? Both

[Liquid_force]

Hi,<br />I'm in the process of rounding up parts for spring maintenance.<br /><br />I've had my boat now for two seasons (beginning season 3). It '89 with a 4.3L OMC cobra. In that time I've had to have the lower unit gears replaced. It had an occasional "clunk" from the time of purchase - so in hindsight that was probably an accident waiting to happen. I've come to the conclusion the previous owner(s) did not exactly keep up on preventative maintenance.<br /><br />My current concern -- it has (and has always had) a vibration that's most noticable at slow speeds - even moreso when turning. It is much less (not) noticable at cruising speed/WOT.<br /><br />When I first removed the drive (end of season 1) I inspected and greased the gimbal bearing, rotation seemed perfectly smooth. While inspecting the u-joints I found them to move very freely as well, but I noticed one of the grease fittings was actually broken off just above the hex. I replaced it, lubricated, and reinstalled the drive. Vibration hasn't improved.<br /><br />Would my best bet/solution be to just replace them both, or is one or the other more likely to be the problem?

 

[Don S]

Re: OMC - Vibration, u-joints? gimbal bearing? Both

It could still be bad ujoints. You could take them apart and inspect the cross piece for groves worn in the bearing surface.<br />You may also have a bent prop shaft or a tweeked blade on the prop that causes the vibration.

 

[Liquid_force]

Re: OMC - Vibration, u-joints? gimbal bearing? Both

Originally posted by Don S:<br /><br />You may also have a bent prop shaft or a tweeked blade on the prop that causes the vibration.

Had the prop rebuilt b4 last season.<br /><br />It feels like a bad u-joint to me too - the vibration is more noticable during low/non-linear torque, but when I replaced bad ones in my car they were so stiff I couldn't move them at all.<br />Oh well, a couple hrs work and $50 wouldn't be so bad even if it doesn't fix it. One more possibility eliminated.

 

[marinemech]

Re: OMC - Vibration, u-joints? gimbal bearing? Both

make sure both hinge pins are tight<br />replace u joints with correct oem number as around your modle year there were some changes to u joints and yokes

 

[Liquid_force]

Re: OMC - Vibration, u-joints? gimbal bearing? Both

Originally posted by marinemech:<br /> make sure both hinge pins are tight<br />

The pins in the side of the bell hsg??

 

[marinemech]

Re: OMC - Vibration, u-joints? gimbal bearing? Both

yes sometimes they will become loose and make the exact sound as bad u joints i haven't seen this with cobras but merc's quite a lot