Engine Noise (Yanmar 16 hp 2GM20F)

[Hal9000]

Hi Everyone,

I've got an O'Day 30 with a Yanmar 16 hp (2GM20F). Last weekend while motoring the engine started making a clattering sound so I shut it down immediately. No warning lights/buzzers went off but I couldn't get it started again. I've checked everything that seemed obvious to me - oil level is ok, kill switch is not stuck, coolant is fine, impeller not blocked, fuel in tank.

This weekend with the help of a more mechanically inclined friend I was able to get the engine running again. It seemed fine for about 10 minutes but then the sound came back - slight at first and then gradually getting louder until I shut it down again. It's a clattering/clacking type of sound deep in the engine - very bad I'm guessing! my friend said it may be a rod/piston/bearing but I recorded the sound/video clip below in hopes that someone with more expertise might be able to confirm or give a 2nd opinion.

sound (compliments of Vimeo):
http://vimeo.com/13613396

If anyone has any feedback on the problem/remedy I'd be grateful!

Hal

 

[filthy liberal scum]

sound clip is way too short.

3 seconds isn't enought time to even venture a guess. its possible that it might be a badly worn piston and that when it warms up the clearance is increased and thats when you might hear a piston slap. you might want to get some compression readings. this would give you an indication of wear. if piston is worn then more than likely the rings are shot also. a worn bearing would give you the noise all the time.

 

[Stu Jackson]

Smells, pictures of wiring without wiring diagrams and sounds are impossible to help diagnose on the internet. Your attempt with the sound clip is really brilliant, I'd never seen (or heard??) of that before, well done.

The trick is to know where the noise is coming from as part of the answer.

Good luck.

 

[Bill Roosa]

A mechanics ear

I am ASE certified in all 7 engine performance areas and have worked on internal combustion engines for over 20 years. I've heard this before BTW.
What you have is a noise that is the right frequency to be associated with the crank shaft. That means your valve train is ok.
It is also the hard deep sound that is associated with a largish metal part being slammed around. So crank, connecting rods or pistons.
You said that it happens after 10 minutes and I got the impression that it starts suddenly and does not gradually build to the level that would cause concern. I'm also assuming that the engine is at idle with no load.
This sounds like an oil supply problem.
Before I go guessing I need some more info.
When was the last time you changed the oil, the filter?
How old (engine hours) is the oil now?
After an oil and filter change does the new oil immediately turn black?
Take off the valve cover oil fill and look inside. Is there a light brownish goop anywhere in sight? You should see clean metal parts. Is there any sludge of any color visible on the internal parts?
With the oil fill still off start the engine. Is there smoke/blow by coming from the opening?
And please explain how the noise starts and if the engine is under load when it happens.

 

[Steve Dion]

Hal: If this were my boat/engine, I would contact a certified Yanmar mechanic and have him check out things. I am wondering if it may be something in your transmission?

PS: I would not run this engine again until someone check things out.

 

[threehulls]

Re: A mechanics ear

I agree with Bill. This is almost certainly connecting rod bearings hammering on the crank. The noise is way too loud for piston slap. Since it seems intermittent, I would guess an intermittent lube oil problem. I have the same engine and there is a lube oil pressure warning light and buzzer. Does that go off? Either way, if there is no external evidence of this noise on the engine I would pull it and have it rebuilt before something major breaks.

 

[Bill Roosa]

I did not indicate what I think it may be

There are several other things that could be going on.
A small leak in the head gasket would also make this sound as the piston tries to compress incompressible water (basically you have a super high compression engine) which then turns to steam and makes a massive knocking noise. There are other things too but we need Hal9000 to answer some questions first before we go tearing things apart.
The fact that it comes on gradually as the engine heats up makes me think it is more along the line of the head gasket leak than an oil problem. An oil problem would happen all the time not just when it is hot. The extra pressure in the water jacket would make the sound get worse as the engine heats up.

 

[Alex Dare]

bad noise

Hate to say it but sounds like it's getting ready to throw a rod. Check the oil for for shiny bits and maybe pick up a simple mechanical oil pressure gauge at the auto parts store. Hook it up in place of the pressure sender/switch and see if it reads up to spec when hot. Bad noise, low oil pressure reading and shiny bits....time to rebuild.
Hopefully just a head gasket issue but I doubt it.