'97 Merc 3.0 LX noise in back of engine

[wayne22]

Hi all,

There's a clacking noise between the back of the engine and the transom. It's been going on for about 1 year. Brought the boat to the dealer last year and they changed the gimbal bearing(it was bad). Noise is still there. I thought maybe the exhaust shutter, but seems the noise is more towards the coupler or in that area.
The noise is only in low rpm, noise stops when you turn the steering wheel and starts again when it's turned all the way to the left or right and when it's in low rpm. Noise doesn't change when you put it in gear or raise/lower drive unit.
I brought the boat today to the dealer and they pulled the drive out, and said the coupler is fine. They think it might be a valve that is stuck. How could the noise stop when you turn the steering wheel if it's a valve problem? Is this possible?
Any help is appreciated!

Thanks,

 

[Don S]

Re: '97 Merc 3.0 LX noise in back of engine

Ujoints...........

 

[wayne22]

Re: '97 Merc 3.0 LX noise in back of engine

When you pull the drive out, how can I tell if the u-joints are shot?

 

[skibug]

Re: '97 Merc 3.0 LX noise in back of engine

It's either the U-joints or the gimbal bearing. Either way both usually start to go bad when water gets into gimbal bearing housing or bellows. Pull the outdrive off and you can reach in and feel if the gimbal bearing is bad. Excessive wear in the U-joints will cause sloppy movement. It should be smooth and tight. Another way to check the U-joints is to see if the noise changes as you tilt the outdrive up and down. Usually the noise will decrease when the drive is down. As you bring the drive up, the u-joints have more binding that takes place and will make more noise as it comes up.

You might also want to check the engine alignment. If the engine alignment is off, this can cause the gimbal bearing to wear out also. If your U-joints are bad, check for water intrusion. If you have some water in there, you will need to find out why and it's a good idea to replace the gimbal bearing.

 

[wayne22]

Re: '97 Merc 3.0 LX noise in back of engine

The boat is at the dealer. He pulled the drive out and says it's not the u-joints. Actually everything in the drive is fine. He's pretty sure it's a stuck lifter. Reason being is when I rev the engine, the noise goes away... more oil makes it way to the upper part of the engine therefore reducing/eliminating the noise level. When i'm in the process of turning the steering wheel, it's under a load and noise goes away. I hope he's right and found the problem and fixes it soon.

 

[Don S]

Re: '97 Merc 3.0 LX noise in back of engine

I'll bet you after all his valve adjusting and everything else it will still do it.

Before going to all that work, have him pull the exhaust riser and check the exhaust shutter.
The original ones were Stainless steel with a rubber coating. When the rubber wore off or melted off from an overheat the shutters would sometimes rattle at idle. But when you speed up, the exhaust holds it open more so it doesn't rattle.

 

[wayne22]

Re: '97 Merc 3.0 LX noise in back of engine

Thanks Don,

That's what I thought it was at first...the shutter...but I listened with a mechanics stethoscope and seemed like the noise was somewhere else closer to the flywheel and coupler area.

 

[Reel Poor]

Re: '97 Merc 3.0 LX noise in back of engine

Maybe the rear motor mounts are bad, or not assembled correctly, and the bell housing is making contact with the transom shield.

 

[wayne22]

Re: '97 Merc 3.0 LX noise in back of engine

Very good possibility also!
I'll check with the dealer tomorrow to see if they fixed it yet. If the lifters are not the problem, i'll mention the mounts and the shutter as the other possibilities for the clacking noise.