Gimbal bearing bad?

[ProfitOfDoom]

Took the boat out today and noticed a sound coming from the back. I read online about people saying you can hear the bearing "growl" when it's going bad when you turn, I assume by growl they mean it's grinding?
Now I'm getting the noise when the wheel is turned but I wouldn't say it's a growl or gring it's more like chatter.
Would that still be the gimbal or something else?

 

[Henry Boyd]

The drive shaft between the engine and the drive is made up of two yokes, two u-joints and an intermediate knuckle. The yoke closest to the engine is about 12" -16" inches long, the other yoke is about half, with most of the shaft inserted into the drive. The end of the long yoke goes into the engine coupling. The other end of the long yoke is supported by the gimbal bearing. So when the drive is down and pointed straight ahead, the drive shaft is lined up in a straight line. And the gimbal bearing is seeing very little load. When the drive is trimmed, or turned, the drive shaft is now angled, and the gimbal bearing is under a great deal of sideways load.

As the bearing starts to go bad it will only make noise when the drive is being turned real tight, but eventually it will happen any time the drive shaft is not straight. The noise is going to be more of a rumbling sound as the bearing slowing begins disintegrating.

Get this diagnosed, and if it is the gimbal bearing, get it fixed. Because the bearing holds the engine yoke in alignment, when the bearing goes it allows the yoke to flop around. That in turn does damage to the engine coupling. If the engine coupling gets chewed up, the only way to replace it is to pull the engine.

Henry

 

[sbw1]

You can rule out or in the u joints by putting the transmission in neutral, reving the engine up to 1500 rpms, and then turning the wheel over hard to the left and hard over to the right. If you hear the chatter, or whatever noise you are referring, it is the u joint making the sound. Gimbal bearings make a more subtle noise.

 

[ProfitOfDoom]

I didnt try reving to 1500 hundred,but I went down there and started it up and turned the wheel at idle and no noise. Then I put it in gear then turned it then the noise started when the wheel was at its farthest point,think gimbal,or u joint?

 

[sbw1]

I didnt try reving to 1500 hundred,but I went down there and started it up and turned the wheel at idle and no noise. Then I put it in gear then turned it then the noise started when the wheel was at its farthest point,think gimbal,or u joint?

It's hard to say without hearing it U joints rattle loudly when the helm is hard over at 1500 rpms. The gimbal bearing is something you wonder about for a while, thinking "something sounds a little different than it use to sound." It gets progressively louder for a while before it fails. You should ask an experienced outdrive boater to listen to it.

 

[Henry Boyd]

Either way, the only way to really know what is wrong is to have the drive pulled.

Henry

 

[ProfitOfDoom]

Ok,I made it to the boat today. I reved it up to around 1500 and turned the wheel and Yes there was a rattle when turned hard either way,so I assume it is the U joint.
I guess that would be better then a gimbal bearing as far as cost and ease of maintenece?
How bad is it to replace the U joint? Just take off props,then pull off the drive and the shaft should be right there right?

 

[SevenTeas]

Right. You may need special tools to get the u joints appart. While your in there you might as well replace the bearing anyway. And a new impeller cant hurt either.

Make sure your in forward when you pull the drive off.

 

[Henry Boyd]

Right. You may need special tools to get the u joints appart. While your in there you might as well replace the bearing anyway. And a new impeller cant hurt either.

Make sure your in forward when you pull the drive off.

Disregard most of the above as applicable for an Alpha, but wrong for a Bravo.

1. DO NOT shift a Bravo unless the engine is running. You can damage the shift mechanism.

2. Bravos do not have impellers, raw water pump is engine driven.

Henry