Yanmar 3HM35

[Ocean Girl]

We left for the Bahamas! Four hours later our yanmar overheated to the point it stalled then caught fire . I was able to put out the fire very quickly thanks to a big 10Lb halon fire extinguisher. The engine does not seem to have that much damage, the paint is burnt in some spots but the engine compartment is relatively unscathed! Our mechanic thinks the engine is ok. We won't be able to really start the diagnostics till tomorrow. Key point is the engine stalled, not siezed. No alarms we off but it at least shut itself down.
My question is, what would you look at if your engine seriously overheated?
Thanks
Erika, Brian, and scupper aboard Rain Dog

[robert sailor]

Well the first question is why did it overheat? Run out of coolant? Run out of oil? Salt water pump failure? Depending on how much and how long it was overheated it may have damaged the rings which could result in blowby.

[a64pilot]

You can't overheat an engine to the point of it catching fire, must be the exhaust manifold paint that burned off maybe after losing raw water flow?
I am not doubting the fire, just hoping maybe that it was not the actual engine itself that got that hot, but maybe the exhaust that did, as that would be a lot less likely to have internal damage to the engine.
I assume no clouds of steam from the fresh water cap and or expansion tank?
If no, then it is hopefully likely that the engine itself didn't suffer any overheat as of course a hot one will boil out the coolant just like an overheating car will.

[a64pilot]

Oh, Cudos on the Halon, you saved yourself one heck of a mess and probably a lot of money by not using dry chemical

[a64pilot]

Severely overheat can warp or crack the head and warp and or crack the block.
Both of those would be almost immediately apparent by rough running and or excessive oil consumption and or coolant disappearing and or coolant and oil mixing. I've even seen valves get stuck from excessive heat.
Fingers crossed

[sailorchic34]

Besides replacing the raw water impeller and checking the discharge elbow for restrictions, probably not the problem, but easy, I would do a compression check.

A blown head gasket can cause the engine to overheat quickly. I'm leaning toward a blown head gasket as the hot gases could get the engine hot enough for oil combustion to occur.

Also check the engine raw water strainer for blockage/ flow. But that would not generally cause a fire.

Glad your all ok and the boat is fine. Quick work with the halon.

[daddle]

Also determine why there were no alarms. She should have been screaming for attention.

[Ocean Girl]

Thanks for the replies. She is fresh water cooled. Her coolant plug striped and blew out(?) dumping all her coolant into the bilge. She was running at idle when she stalled. None of our alarms gave us warning BUT her auto shut down did protect the engine by shutting down. I never saw flames, ( I didn't open the access hatch for fear of feeding the situation more oxygen) I did see a hell of a lot of dense dry smoke(grey). The cabin floor was very warm and the engine compartment bulkhead hot. I have pics on our blog post.

"Fire" does seem dramatic, especially after seeing how good the engine compartment looks. but I cannot describe it any other way except "burning with large amounts of grey smoke"..? There was a ton of thick smoke but it was almost immediately out when I hit it with the halon.

Rain Dog | Life Aboard a Pacific Seacraft 34
Thanks
Erika

[GILow]

Sounds a bit like raw fuel spilling onto a hot exhaust manifold to me. The engine shutdown may therefore have been simply fuel starvation?

Matt


Sent from my iPad using Cruisers Sailing Forum

[HappyMdRSailor]

Oh man...

This could be good or bad depending on what mechanism stopped the engine....

1. Overtemp limit shutdown = Good

2. Binding, seizing due to overheat = Not Good...

Somewhat uplifting hearing that the mechanic has high hopes! We'll hope for a belated Christmas gift...

[FSMike]

Note to self: Install guages in addition to alarms.

Ocean Girl - Hope things turn out well (i.e. inexpensive) for y'all.
Have a Happy New Year.

[a64pilot]

Alarm didn't sound as it is a water temp alarm, no water to sense temp, no overheat condition sensed, same for a gauge. Although suddenly losing temp reading on a gauge should alert you to somethings wrong.
Although usually if you let an engine get real hot, oil pressure goes way down due to oil losing viscosity with heat, so watching a gauge, slowly decreasing oil pressure may mean an overheat.
I doubt there is an auto-shutdown is there? Usually auto-shutdown equipment is only on engines that are un-monitored like an irrigation pump, what triggers auto-shutdown is the same switches that trigger an alarm, high temp, low oil pressure.
No, I think she got so hot it shut down due to excessive friction, hopefully it didn't fully seize though.
I assume she will turn over and start now?
Once you get her running again, I'd change the oil ASAP, it's possible it got so hot it may have changed it's properties and oil is cheap.

[Cheechako]

If the engine stalled and got that hot... I doubt it's OK. A diesel engine doesn't stall without something seizing up to my knowledge.
You need to find the source of the fire though.... seems electrical is more likely but that wouldn't stall the engine.... I don't think.
Is that an old engine? I doubt it has any kind of auto shutdown?
If you are lucky maybe a HP fuel leak occurred and ignited some way? That would shut down the engine without a major seizing.....

[a64pilot]

I took my Brother's 911 Porsche to Brumo's Porsche many years ago to have the ride height adjust to european specs, I think late 1970's.
Was talking to an older gentleman there in the waiting area and he complimented me on the 911, I laughed and told him my car was a 1971 Super Bug, he laughed and told me he had one too. Well be started talking Bugs of course and he told me he only had it let him down once. He was going down the highway at 55 MPH and the car kept taking more and more throttle to hold speed, finally it started slowing down so he pulled over and the car shutdown, tried re-starting it and it would just go clunk, tried checking the oil and he couldn't as the dip stick was so hot, he couldn't touch it, wrapped a rag around it to check it, found no oil on the stick, walked to buy oil and it took three qts to get it to the full mark, cranked it up and drove home.

Well of course I explained to him that the engine seized due to no oil and excessive heat, that is was a miracle that it re-started and ran at all, but it had to have severe damage and would very soon seize again as the bearings at least had to be galled, maybe even the pistons had smeared themselves on the cylinders etc.

He had a funny look the whole time I was telling him this, when I stopped running my mouth, he told me that happened three years ago and it had been running fine since. Yeah I know, one in a million, but some people just get lucky, lets hope Ocean Girl and Rain Dog are one of those people

[roverhi]

The intake for my 3GM30F became clogged and engine overheated. Didn't get any indication of the overheat till gray smoke started pouring out of the engine room. The smoke turned out to be the last of the coolant boiling off. Was running the engine at low rpm when it happened. Shut the engine down, it didn't stall. Got the boat the short distance back to the slip by keeping the heat exchanger full of coolant and running at idle. That was a few years ago and hundreds of hours and the engine is still running fine. The cast iron block and head of the GM series engines will take a lot of abuse. Don't know if that carrys over to the later Yanmar Engines. It's aluminum that warp and crack if you look cross eyed at it.