OK Pelican Braintrust - Boat Engine - Inboard Mercruiser

[JeremyD]

So I have this boat - a Bertram 28 - It was my stepfather's boat -

Twin 1986 Inboards - 260HP 5.7 Mercruisers (1600 hours)

The Port Engine started making this noise - and I can not figure out what it is.

Changed the oil - and filter - no metallic pieces in the oil. (I have not cut open the oil filter - I guess I can do that next)

Changed the water pump - it's new. Changed the fresh water pump - -

It almost sounds like it's coming from the crank pully/harmonic balancer

Other than the noise - the engine runs well - good oil pressure - runs at temperature.

The Manifolds and Risers have been recently changed -

https://www.youtube.com/watch?v=ufS3BQ5w14Q

Any ideas?

[gshase]

It sure sounds outside of the engine block. Like a pulley or water pump or a accessory.

[VINMAN]

Check the Harmonic balancer . I've seen the rubber inserts go bad on those, a number of times.

[stomachmonkey]

Exhaust or vacuum leak.

Sounds different because motor is in an enclosed space.

[afterburn 549]

Unhook all accessories and fire her up (all belts all drives).
-(not for long, just enough to determine)
If no luck - pull valve covers and check for" loose ones" . It sounds too tinny for a rod, but about right for a collapsed lifter .

[JeremyD]

Thanks I'll have to try that

[fastfredracing]

Originally Posted by VINMAN

Check the Harmonic balancer . I've seen the rubber inserts go bad on those, a number of times.

I second what Vin says. When the rubber lets go, the outer ring can move around. I have seen one saw through a timing cover.

[scottmandue]

Originally Posted by JeremyD

So I have this boat - a Bertram 28 - It was my stepfather's boat -

Twin 1986 Inboards - 260HP 5.7 Mercruisers (1600 hours)

I can't help you with the Mercruiser but dayam that sounds like one fine boat!

[asphaltgambler]

From the info and video my opinion: Def something directly tied to crank rotation related and def something outside the block. Like the balancer coming apart or flywheel / flexplate bolts as they connect to the trans. Quickest way as said above to remove drive belts and start engine to see if it goes away or changes. Then go from there to the rear.

[JeremyD]

Originally Posted by scottmandue

I can't help you with the Mercruiser but dayam that sounds like one fine boat!

Thanks for the opinions - I have a feeling it's the harmonic balancer and have ordered a replacement. I'll give an update

Here's a picture of the boat

[edgemar]

i like the boat and the dog too!

Good Luck...hope it's the harmonic balancer!

[JeremyD]

Yep - Harmonic Balancer - thanks for the advice - not too much drama getting it off - you can see where it was wearing on the timing chain cover (and obviously making noise)





Thanks again for everybody's input!