Thought my gimball bearing was shot but its not now what?

toy4x4

Seaman Apprentice
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Jul 26, 2011
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31
I have been hearing a loud roaring sound with stern drive up or turned... and when slightly revving the engine. Been seeing some water coming in the boat also... So figured it was the bellows and gimball bearing. I pulled the lower unit and checked the water pump... it looked new as well as the gaskets and plates. I pulled the upper half off the bellhousing and looked inside. The gimball bearing looks new and so do the bellows. No signs of water entering the drive bellow anywhere. The bearing still has clean fresh grease smeared where a gob of grease wiped off of the drive shaft during assembly. My U-joints look nice and clean like they are new also. No play or slop in them either. No rust anywhere. I can spin the bearing with my fingers and it spins freely and smoothly no play or roughness. Any Ideas?

Can I run the motor with the drive off to see if I get the same roaring noise?
Could it be that my bearing just needs greasing if so how do I grease it?

Its a 95 Alpha 1 gen 2
 

Don S

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Aug 31, 2004
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62,321
Re: Thought my gimball bearing was shot but its not now what?

You can't just look at a bearing and tell if it's good or not. Reach in there and turn the gimbal bearing. Is it perfectly smooth? Any roughness indicates a bad bearing. Could also be faulty ujoints, you can't always feel them and tell if they are bad or not.
With the drive off, you can start the engine and run it for 15 or 20 seconds without water, that should be enough to tell if the noise is gone.
 

makonnen

Petty Officer 2nd Class
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Apr 4, 2012
Messages
184
Re: Thought my gimball bearing was shot but its not now what?

Even when you grab the bearing and turn it, the problem may not show up. Sometimes a bearing won't make noise unless its under normal load.

Try running the engine without the accessory belt too ... this will help isolate the problem.
 

toy4x4

Seaman Apprentice
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Jul 26, 2011
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Re: Thought my gimball bearing was shot but its not now what?

Ok I will try to post some pics of it this evening. I took some last night but left camera at home... I swear the bearing looks as if I just put it in there yesterday... I thought water had to get into these to kill them but maybe it was installed wrong maybe someone hit on the inner race while putting it in IDK? I can spin it by hand and it feels silky smooth. Anyways I will run the motor some tonight and see. Just by the looks of everything (bellows, bearing, shaft, ujoints, and water pump, and gastkets). I'd guess all of this was done a year or so ago. I bought the boat near the end of last summer so this could have been done last spring or winter before.
 

Don S

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Re: Thought my gimball bearing was shot but its not now what?

Like I said, run the engine with the drive off. That will eliminate the engine as the cause of the noise if the noise goes away.
 

toy4x4

Seaman Apprentice
Joined
Jul 26, 2011
Messages
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Re: Thought my gimball bearing was shot but its not now what?

Ok ran the engine and could still hear it. Pulled the belts and it went away. Spun the water pump (one on front of engine 4.3l v6) and could feel a rough bearing and could hear the roar. Can also feel a good bit of play in the bearing besides the normal in-out slide that these GM pumps tend to have. Looks like it may have a slight leak also as there was some rust underneath it and some rust stains down the timing cover and on the crank pulleys below it. This would explain the water coming in the boat also.

Can I replace this water pump with a automotive one from a similar year GM 4.3 v6? Or is there a difference like hose connections or brass impellas?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Thought my gimball bearing was shot but its not now what?

Can I replace this water pump with a automotive one from a similar year GM 4.3 v6? Or is there a difference like hose connections or brass impellas?

You can't use an Automotive pump unless you have closed cooling. The marine pump has a cast brass impeller and a stainless steel seal housing and backing plate...If you can find a new seal and bearing you could just strip down the old pump and rebuild it with new bits. I used to do that to water pumps years ago, but I can't seem to find anybody selling just the parts anymore.... Way of the world I guess... Throw-away society :mad:

Chris......
 
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