Mercruiser 5.0 noise - listen to video

[joe from ny]

It's a 1995 mercruiser 5.0 with about 630 hours. Had flywheel and starter replaced beginning of 2014 season. No problems that season. Boat went to marina at end of season for winterization and beginning of 2015 season had this noise upon first receiving boat back. I pulled each spark plug one at a time. No difference. Oil pressure is fine. Oil looks good. Boatyard claims it is main bearing and I need a rebuilt motor job at $7,500. Since they screwed up every other job I had them do I think they are wrong. What can it be? Check out the video. http://youtu.be/jhe9p3L2kxo

http://youtu.be/iAzgWnKb5_Q

 

[Bondo]

Boatyard claims it is main bearing

Ayuh,.... Did ya ask just How they came to that conclusion,..??

Donno what it is, but I've never heard a main bearin' make such a noise,....

What's the oil pressure of the motor,..??

 

[Bt Doctur]

rhythmic . more like a bad rocker arm or bent pushrod. pull the valve covers to inspect the valve train.

 

[Rick Stephens]

That loud of a main would have somewhere right around zero oil pressure.

 

[funk6294]

Its sounds more like banging sheet metal. Is the flywheel cover loose and hitting the flywheel?

 

[joe from ny]

Sorry, I forgot to mention in pursuit of elinating possible causes, I had both heads off and the valves done. So the heads, valves, springs, and head gasket are good now. While the valve cover was off, it looked like the lifters were all working properly. Also I pulled each spark plug one at a time, no difference in sound. Oil pressure is fine and oil looks normal on the dipstick. And one guy I had look at it said maybe something on the flywheel worked its way loose and the noise comes from the bell housing at the rear. But I only had the issue this season, not last season after the flywheel was replaced. The issue started my first day of starting the boat after they got it going and left it in my slip. They do remove the out drive unit for the winter. Could they have done something wrong upon reassembling it to the boat?

 

[funk6294]

Hard to say if they did anything wrong. Usually a drive install is pretty straight forward and doesn't require touching anything inside the boat short of putting the shifter in forward. I would see if you can reach around under the motor to see if the flywheel housing cover that goes across the the bottom of the flywheel housing is loose. Its possible the a couple of bolts or the cork gasket were omitted which cause it to rattle.

 

[Fun Times]

Knowing they had the flywheel off at some point, it's possible that one of the flywheel or engine coupler bolts has started to back out hitting the bell housing....Pretty sure there's another video somewhere online/iboats with the same type of sound that turned out to be a bolt hitting the bell housing.

Besides the noise, how does the engine seem to run?

You could try grabbing the front crankshaft pulley/damper to ensure it doesn't move in and outward indicating a crankshaft type problem.

Hope it's an easy one, good luck.

 

[alldodge]

Noticed in the vid that the noise went down when closer to normal idle and got loud when idle was increased.

They do remove the out drive unit for the winter.

Do they remove and leave it off, and if so why?
Does sound to me in the flywheel area

 

[joe from ny]

Noticed in the vid that the noise went down when closer to normal idle and got loud when idle was increased.



Do they remove and leave it off, and if so why?
Does sound to me in the flywheel area

they take it off and store it inside where it is warm.

 

[Rick Stephens]

Something that tinny and loud should be really easy to isolate by using a broomstick and touching it to different places while touching the other end to your ear. Even better than a stethoscope with it that loud, hurt yours ears with a stethoscope. I've heard engines do that kind of thing when they ate a nut in one of the cylinders. I can see a half threaded out bolt inside the flywheel cover doing that as well. All better than an inside component. One can hope anyway.

 

[alldodge]

they take it off and store it inside where it is warm.

That is the first time I heard of that, Do they really need a blank'ey (sorry had to say it ound: I'm a bad boy). Doing that for everyone makes me wonder if you got your original drive back. Could be something as simple as they gave you someone else's drive which is bad, just doesn't add up for me

 

[JustJason]

You can always do a cylinder drop test and see if the noise goes away or lessens.... That will tell you if it's a bearing/con rod/piston issue..... Or something else like some of the other guys have mentioned. With a pair of insulating pliers it takes all of 5 minutes to do on a V8.

 

[Bt Doctur]

Look at whats rotating. pistons, rods, bearings, flywheel coupler . If you confirmed the heads and valve train were good then pull the drive and test run again.
If you have the room ,remove the spark plugs, get a piston to go just past TDC on compression or firing stroke ,
insert a rod or screwdriver and try to move the piston downward. If it moves, the rod bearing is destroyed
the coupler bolts are about an inch and 3/8ths . they have been known to back out if Loctite was not used. flywheel bolts, not likely.
worst case is remove the engine for inspection

 

[Bondo]

You can always do a cylinder drop test and see if the noise goes away or lessens.... That will tell you if it's a bearing/con rod/piston issue..... Or something else like some of the other guys have mentioned. With a pair of insulating pliers it takes all of 5 minutes to do on a V8.

I pulled each spark plug one at a time. No difference. Oil pressure is fine.

Ayuh,.... He says he did that, which is why I'm doubtin' a rod bearin',......

 

[joe from ny]

No Title

I was just trying to rule out any issues that could be fixed without taking the motor out. When they put it back in the boat after the flywheel and starter job, they hit the back of the engine hatch opening with the distributor cap and broke an electrode tower. Just cracked it and left it broken at a 45 degree angle. They never even noticed it during their winter service. I only spotted it when trying to diagnose my current issue.

 

[Rick Stephens]

Probably even ran ok with the dizzy cap busted.

 

[Mischief Managed]

Take the belts off and run it again to see if it's quiet. Might be the circulating pump. I had one fail suddenly and it sounded like that.

 

[joe from ny]

here is the latest video, before i pull the boat out of the water this week.

 

[thumpar]

I would pull the drive off and test that way just to rule that out. It sounds like a valvetrain problem to me.