Mercruiser 140 strange noise

[Rick-101]

Mercruiser 3.0l 140 1986 with Alpha one aligned, greased with new gimbal bearing and fluids.
Project boat. Engine was torn down; carb rebuilt, fresh fuel and filters, plugs changed, points cleaned, dwell adjusted, timing and rockers adjusted and rechecked. Running without flame arrest.

VID 00000008 - YouTube

I'm stooped. Unless the back of the flywheel housing shield needed a gasket and is rattling or slight oil overfill.
I can't figure out what this noise might be.
It seems to be predominantly mid range. Noticed I get a very very slight hesitation before top speed on wot at the top end of the rpm range.

Your guesses are greatly appreciated,
Rick

 

[Bt Doctur]

Re: Mercruiser 140 strange noise

If your doing that on a hose you need a new impeller too.
Cant hear anthing out of the ordinary for a 4 cylinder. A high rpm rattle on those motors is usually a cracked flywheel dust cover
if it is a metal one.

 

[Starcraft5834]

Re: Mercruiser 140 strange noise

I've got a 1987 3.0 140. looks like same engine as mine,, and sounds same,,,,I dont hear anything, sounded tight..

 

[Rick-101]

Re: Mercruiser 140 strange noise

It was on the lake it took the video, 140psi on all four cylinders. I never got to hear the engine before it had to be pulled. I was worried something was wrong or she was running lean.
Thank you!

 

[Silly Seville]

Re: Mercruiser 140 strange noise

I've had three boats with that engine (2.5 and 3.0) Yours sounds healthy to me. They do rattle like that when under a load. Just the nature of that particular engine. They are noisy, not smooth like a V-8. I believe your engine is fine. Enjoy!