Mercruiser 5.0 noise - video - what is it?

[Cheechako]

Well....... if it's the GM based 5.0 motor it is readily available. I checked a couple years ago and a rebuilt longblock was only $1575. (Jasper engines) That's the nice thing about the GM based power plant... there were so many built for cars and trucks.
Be sure to check out the powerboat forums mentioned earlier, those guys know this stuff like the back of their hand...

[GPSocal]

Joe,

It sounds like valve train noise which could be stuck valve or lifter. Try the old yardstick in the ear method to try and isolate the noise. Good luck.

[captain mitch]

Ahhh, Has anybody considered the springs in the vibration damper? If the damper plate is orig 1996 it just could be rusted and falling apart springs

[Joe from ny]

where is the vibration damper located?

[knotnow]

From the sounds on the video a lot of the noise sounds tinny and inconsistent. My guess it’s under the inspection plate at the bell housing area. The lower spectrum sound could be a longer than original bolt mounting the flex coupler to the flywheel hitting the block.

[jimbunyard]

Originally Posted by captain mitch

Ahhh, Has anybody considered the springs in the vibration damper? If the damper plate is orig 1996 it just could be rusted and falling apart springs

Originally Posted by Joe from ny

where is the vibration damper located?

Believe the vibration damper Capt mitch is talking about is the coupler between the flywheel and the outdrive. It is mounted on the flywheel under the flywheel housing. There are no springs in it. This is what it looks like



The torsional vibration damper is located at the front of the engine and is mounted on the crankshaft. The crankshaft pulley is bolted to it with three bolts and a center screw.

Sorry to hear about the second ahole at the marina, as noted those engines are readily available from a variety of sources, in a variety of states of build, at a variety of prices (should it come to that).

Took a quick look at Jamesport on Google earth, Long Island may not be the place to find the most uh...economical... boat mechanics. I'd shy away from marinas and try and find an independent with a good reputation, maybe talk to a Mercruiser rep for advice, or someone from a local boating organization or club.

As a long shot, after listening again I wonder if it might be a problem with the exhaust manifold. Loose bolt or warped flange or bad gasket between the manifold and the head? Water does not flow into those manifolds from the heads, there could be an exhaust leak that is hidden, intermittent and/or dependent on certain pressure conditions to make itself audible.

[HappyMdRSailor]

That noise is "low" and "deep" in the engine... Seems timed at crank speed...

To me, it seems that...
If it's not a rod bearing.... It's the aft end of the crank/U-joint/flywheel...

[Juho]

Check also the engine support, i.e. the connection between the engine and the hull and dampers there. (I don't exactly know what those components are called in English) We once had a noise and vibration problem coming out from there (not in a boat though).

[Siberianhusky]

Take a length of broom stick and put one end on the block one end to your ear, acts as a stethescope(?), you can isolate where the noise is comming from by testing different spots on the block, valve covers etc.
Long handled screwdriver works well for areas easier to reach. Put the plastic end to your ear!
Honestly can't believe somebody hasn't suggested this already, one of the oldest mechanics tricks in the book for diagnosing engine noises.

[Joe from ny]

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. This photo is after I tried to jam it back on. It was quite skewed initially. The cap was new that season also.



Sent from my iPad using Tapatalk

[Joe from ny]

That's why I don't go anywhere near that yard again.


Sent from my iPad using Tapatalk

[Joe from ny]

Here is a new video I shot today with the camera closer to the motor.
https://youtu.be/lsU9zwnSMlA


Sent from my iPad using Tapatalk


Sent from my iPad using Tapatalk

[Cheechako]

Originally Posted by Joe from ny

Here is a new video I shot today with the camera closer to the motor.
https://youtu.be/lsU9zwnSMlA


Sent from my iPad using Tapatalk


Sent from my iPad using Tapatalk

When you slow the engine down it really starts sounding like some kind of rocker/tappet noise. Pretty loud and heavy though. It's a tough one , but I would likely be looking under the rocker covers first. Almost sounds like a bit of exhaust leak mixed in there too... Could be a rod I suppose... bottom line is it sounds related to one cylinder somehow; rod, rod bearing, valve, pushrod issue... etc

[Siberianhusky]

Try the broomstick! Tough crowd!
https://www.gunandgame.com/threads/r...to-tell.96429/
Here's a video about it
Engine Stethoscope Using A Broomhandle

[HappyMdRSailor]

Originally Posted by Cheechako

When you slow the engine down it really starts sounding like some kind of rocker/tappet noise. Pretty loud and heavy though. It's a tough one , but I would likely be looking under the rocker covers first. Almost sounds like a bit of exhaust leak mixed in there too... Could be a rod I suppose... bottom line is it sounds related to one cylinder somehow; rod, rod bearing, valve, pushrod issue... etc

man that is a tough one.... Sounds higher up in this video than the others...

The good news is that if you keep running it, there will be enough wear evidence to find it easily!

Go to Autozone/Advanced/O'rielly and pick up one of these...
Amazon.com: Lisle 52750 Stethoscope Kit: Automotive