Nasty noises from Yanmar 4JHE

[Kamaloha]

Underway for two hours Sat AM in a dead calm. All of a sudden REALLY nasty noises coming from powerplant - like I was driving a gravel road with a string of tin cans behind me. Shut down immediately and checked for a lobster warp in the prop. Nope - all clean. Operating temps normal, oil and coolant normal, none of either in pan below engine. Removed belt and spun alternator and coolant pump, all quiet. Started engine in neutral, engine ran but still had the ugly noises, shut down right away.

Engine is ca 1988, approx 5300 hours on it, last changed oil and coolant at haulout this winter. Has never burned oil or given me any problems. I tend to run on the lazy side, about 2100 RPM where it was this day; any harder and it seems like the prop is cavitating, at least it gets a lot noisier and 2100 is plenty for hull speed in calm conditions.

Any thoughts on what I'm looking at? I'm stranded about two days sail from home, and the local mechanic will take a look tomorrow. I just wanted a heads up. Since the engine was in neutral on the second start, don't think it could be the tranny - or could it?

[Inthewind]

A bolt may have backed out of your drive plate or the head of a bolt could have broken off. Maybe a broken spring on the drive plate. A bolt,bolt head or spring could be going around and around the fly wheel and making a noise like you describe. I would guess that it is not your engine making the noise but drive plate or transmission related failure.

[hellosailor]

Hopefully the mechanic will tell you if the noise is really from the engine or from the transmission. If it is the engine...noises like "gravel" or "silverware in the dishwasher" usually mean broken metal parts. Springs, valves...if you are lucky the mechanic is both competent and honest and he can access the broken bits without huge amounts of time.

Shutting it down fast was the right move.

If, for whatever reason, you don't feel comfortable with the local mechanic...either sail it home or get yours to come out. "Competent and honest mechanic" is all too rare these days.

[senormechanico]

Years ago, I had the same sound coming from my Yanmar 3HM35.
A couple of minutes later the belt screamed and the engine stopped.
The fresh water pump had seized.

Steve B.

[Alan Wheeler]

My money is on Inthewind. I would say you have an issue with teh drive plate. This plate is mounted on the flywheel and connects the Transmission. It is desinged to minimise the "injector shock" that is transmitted through the engine train to the gearbox. Spings are mounted around this plate to do such. These plates can fall apart over time and you will eventually lose drive all together once it finaly disintergrates.

[Kamaloha]

Thanks for the reassuring words. I hope you are right and that it is something between engine and tranny. While access will be a b**ch at least this means I won't have to think about repowering in the middle of the short Maine sailing season. I'll post when I know what they found.

[senormechanico]

Good luck on your search. It would be an easy first test to remove the belt to see if it is the fresh water pump bearings or not. No further disassembly required; just a quick engine start would tell you whether or not you're on the right track.

Steve B.

[migot1]

it can be one piston got loose...it happened to me 2 years ago...get of the top part of the engine, and turn the engine slowly, if one of the piston is free , you shall see it right away

migot1

[senormechanico]

I re read your first post. I must have missed your statement about spinning the alt and pump. Duh.

Steve B.

[Alan Wheeler]

Migot, just to be clear, a Piston can not get loose. A big end can which is what I am assuming you are talking about. This causes a very nasty knocking sound. I am not sure, but I don't think this is what is being descirbed.
But Kamaloha, you maybe able to do a little test with a long shaft screw drive pressed to the ear. Place it on variouse points of the engine and listen. You will hear noises around the engine and in some situations this method can help zero in on an area making more noise.

[hellosailor]

"a Piston can not get loose."
Mental picture flashes, of Woody Allen and whats-her-name in Annie Hall, where he's chasing a lobster that gets loose and hides behind the refrigerator.[g]

I think the poster meant, if the connecting rod breaks, the piston "gets loose" from the works, even if it is still in the cylinder.

Without knowing what's banging around...I wouldn't run the engine until someone experienced was there, so they could run it for the shortest possible time, and mitigate any further damages from whatever is running around in there. Pistons, springs, lobsters....[g]...

[Alan Wheeler]

I had a vehicle come in to work last year. It had a bit of a knocky noise. It started fine, idled like a dream, but had this noise. I gave it a quick rev up and there was a loud bang and smoke every where. The big end bolts had parted company and the result was the conrod being shoved through the cast block of the engine blowing oil everywhere. Interestingly, the engine still ran fine, although on only 3 cylinders.

[Kamaloha]

I just heard back from the mechanic. As Alan surmised, Inthewind got it right; the damper plate has self-destructed. From what he said the metal flying around has damaged the starter bendix and possibly the bell housing too. Better than the whole engine, I suppose...

[Maddog]

Same thing happened to me after a high reved shift from reverse to forward, (You'll have to buy me a beer if you want the full story. Let's just say it envolved a cross wind, narrow channel and the "Lucky Lady"). I had to have the whole tranny rebuilt. I think it was due anyway.

[hellosailor]

"Better than the whole engine, I suppose..."

MUCH BETTER. The Bendix...OK, a starter is still cheaper than an engine. The bell housing...is mainly cosmetic, it really is just there to make sure all those flying metal bits don't come flying out at you. [g]