Mercruiser 140 rattling

[m*a*baity]

Finally got the money pit running. I noticed a rattling noise at higher rpm. Took it to the lake and as the day progressed rattling noise got louder. I'm idling fine fires up and runs great. 4200 rpm wot and she runs great from idle to wot. The noise eventually got louder and now it does it at idle too. Have looked everywhere on the engine, no loose bolts. i touched the oil pan and could feel a vibration on the oil pan that matched the noise. Any suggestions? Gimbal bearing has been replaced, impeller in out drive. I've spent more hours wrenching on this thing already than I have i the water. Any advice would be appreciated!! Thanks

Oh it is pouring oil from the valve cover. leaked out 2 qts in a day. Doesn't smoke other than a little fuel burn off. Put oil back in when it said "add 1 qt"

 

[APPALOOSA2]

Re: Mercruiser 140 rattling

Sounds like you have leaked oil too many times and ran it low. When a engine loses oil the oil pressure will start to go down and when you try to get that boat up on a plane and you are down that much oil you will have NO OIL till it levels out again.

Why didn't you just buy a valve cover gasket and fix it , it's much cheaper and cleaner than buying oil all the time.

I would suspect the rings have worn down quite a bit from lack of oil and valve train. Do a compression test and see where your engine is at.

 

[m*a*baity]

Re: Mercruiser 140 rattling

It's not smoking any at all other than a little gas burn off. No oil smell to the exhaust. At certain rpms it is quiet. When it is under load no noise. only when i have reached speed and cruising. I have a gasket on the way. do you think the gimbal wasn't properly installed? Wood it make that type of noise? Also my shifting is in a bind. it doesn't want to come out of forward or reverse. it will when I make it. Can a noise from the outdrive or transom come up through the engine? Thanks

 

[MikDee]

Re: Mercruiser 140 rattling

I've heard rattling from loose vibration damper (crankshaft pulley) bolts, on a 4cyl, Check them out.

 

[m*a*baity]

Re: Mercruiser 140 rattling

I did find a bolt laying underneath the engine. I will check that. Thanks man

 

[Bt Doctur]

Re: Mercruiser 140 rattling

Check the flywheel dust cover for cracks if it`s rpm specific

 

[m*a*baity]

Re: Mercruiser 140 rattling

I think I've found it. My alternator bracket was loose and missing a bolt. When the rain dies down I will put it back together and try again. I hope that's what it is. It sounds like metal against metal vibration. My skid plate on my ATV used to make a similar sound at high revs. Thanks fellas

 

[m*a*baity]

Re: Mercruiser 140 rattling

I think I've found it. My alternator bracket was loose and missing a bolt. When the rain dies down I will put it back together and try again. I hope that's what it is. It sounds like metal against metal vibration. My skid plate on my ATV used to make a similar sound at high revs. Thanks fellas

Fixed this and still rattling. Thinking maybe rod bearings. The noise id really loud and is coming out of the oil pan. Also I can feel vibration that matches the noise. Guess I'll pull it back out again. My new profession "Boat Mechanic". One day I will take up water skiing! Gotta love it!

Man, I tell you what...

 

[m*a*baity]

Re: Mercruiser 140 rattling

Engine coupler was loose and the flywheel was smacking against the shield/inspection plate. tightened it all back up. gonna have to replace the inspection plate. safe to temporarily run without it?

 

[MikDee]

Re: Mercruiser 140 rattling

Engine coupler loose? Good luck, Don't know if it's safe to temp. run without it?

 

[APPALOOSA2]

Re: Mercruiser 140 rattling

Glad to hear you found the problem. It would be safe to run, but make sure there is no wires hoses or anything loose that could roll back there.
I wonder why it loosened up, did you replace it at one time ?

I would probably blue loctite the coupler bolts.

Make sure you replace that cover don't just let it go, someday you will get something back there and wished you had replaced it.

 

[Flemingball]

Re: Mercruiser 140 rattling

You seem to know your stuff. Is the shroud cracking a common problem? I have a 1974 3.0 Merc w/pertronics Base timing is 2 degrees btdc, total advance is 35 degrees and is there at 2000 rpm. Recent head gasket replacement. Runs great but rattles like a bugger from 2000-3000 rpm. Its as if it turns on and off at those rpms. Runs great otherwise. I cannot find total advance specs for my particular motor but see on numerous posts where total advance for the delco est and one other thread all say approx 27 degrees total advance. Any thoughts? I appreciate any help

 

[trevtt600]

Re: Mercruiser 140 rattling

I have the same rattling noise on my 140 mercruiser. between 2000 and 3000. Have just kind of got used to the noise. If you find out what the noise is, i would love to hear.

 

[Toonafish]

Re: Mercruiser 140 rattling

Guys...I too was getting a noise and could not pin point it (1989 Merc 3.0) similar to many others here. After many hours of research reading threads of people having the same problem,I went back to my engine and did a little troubleshooting. When running I would get a rhythmic clanking noise low and at the aft end of the engine, it would come and go at middle range rpms. I touched the starter, and could feel the vibration. When I applied enough pressure the noise went away. I checked the mounting bolts for security and also confirmed the forward support bracket was installed. It was when I was checking the mounting bolts I discovered the dust shield flexes ever so slightly (discovered by accident). When pushed and released it hits the starter housing where the inboard mounting bolt is located making an audible click. I placed a piece of rubber gasket material between bolt and dust shield...Problem solved! Purrs like a kitten.

Hint: I found my problem by laying on the boat floor on the opposite side of the engine from the starter, there is relief bend to accommodate the inboard starter mounting bolt you can see with a flashlight. Push and release the dust shield slightly. You can feel the metal to metal contact with your fingers after releasing when the shield is flexing back into place . In my case I could hear it too. I suspect this is an area where cracks in the shield may occur as stated by Bt Doctur. Mine fortunately did not.

I am just glad it wasn't something internal. I can see where this can be easily misdiagnosed as rod knock, u-joints, etc leading to major drinking problems.