Loud rattling noise 4.3L merc

[scotterman]

i was out wake boarding yesterday and the engine was running fine. Ive just changed the drive fluid. all of the sudden there was a loud clanging noise coming from under the engine toward the back...do you think it may be the bearings in the out drive.. has anyone else had this problem?

 

[havasuboatman]

Re: Loud rattling noise 4.3L merc

How much and what kind of oil did you put in the drive? Are you sure the rattling noise isn't your exhaust flaps in the Y-pipe? Has the boat over heated recently?

 

[Bt Doctur]

Re: Loud rattling noise 4.3L merc

My goodness, heard it all the way to NJ, horrible sound. might be the drive or the gimbal bearing. when was it serviced last?

 

[scotterman]

Re: Loud rattling noise 4.3L merc

i just bought it a week ago. i put the high performance drive fluid in until it came out of the top hole. it hasnt been serviced in a while. i just took it out again to see if i could hear where the noise was coming from and it just sounds like something is bouncing around in the engine. i have a 96 regal with the same alpha one drive that i could switch out, but if it is the gimbal bearing, how would i get that out? if i switch the drives would that bearing come out, or is it in the engine somewhere?

 

[havasuboatman]

Re: Loud rattling noise 4.3L merc

The gimble bearing is mounted in the transom assembly. It doesn't come out with the drive.
But, the gimble bearing , when it goes, makes more of a growling noise.
Stick a grease gun on the zerk fitting on the starboard side of the transom assembly and give 5 or 6 good pumps. If the bearing is the culprit, that grease will greatly reduce the noise while running. If it goes away, you found the problem. If not swaping out the drives would be a good way of ruling out the drive. If the noise is still there with the new drive, your exhaust flaps in the y-pipe are likely the cause. They make a LOT of noise when they need replacing.
While you have the drive off, reach into the opening where the u-joints go. That bearing is the gimble bearing.

 

[scotterman]

Re: Loud rattling noise 4.3L merc

the sound definitley isn't growling...it sounds more like a big chunk of metal bouncing around inside the engine...

 

[havasuboatman]

Re: Loud rattling noise 4.3L merc

It is most likely the exhaust anti-surge flap in the y-pipe. You will have to pull the risers in order to look down into the Y-pipe.

 

[scotterman]

Re: Loud rattling noise 4.3L merc

is that a fairly easy task? do you have any kind of diagram? or maybe somewhere online that shows how to do it... i'm pretty mechanically inclined but just not sure exactly where it is located

 

[Silvertip]

Re: Loud rattling noise 4.3L merc

You do know what an engine miss sounds and feels like? Rocker arm came loose/broke for example. You have monitored the instrument panel and engine temp and oil pressure are normal?? Have you opened the engine cover and actually tried to get a little closer to the noise as in engine proper, transom area, or outdrive. Use a stick as a stethoscope to try and isolate the location.

 

[scotterman]

Re: Loud rattling noise 4.3L merc

the sound isn't always there, but it's coming from the bottom of the engine it seems. as soon as the noise stops, if i turn the motor left or right it comes back... the temp and pressure are normal.