Mysterious Engine Failure

[LeighWebber]

Long post warning. What follows is a description of a mysterious engine failure. I’ll post detailed background info and a description of exactly what happened, then invite you folks to figure out what caused the problem. After we get a few suggestions, I’ll post the actual cause of the failure, which took me by surprise.

Cheoy Lee Offshore 32, Beta 25 diesel engine, 580 hours. Immaculately clean and in perfect condition. Dripless shaft seal with a sea water feed teed from the engine sea water exit hose close to its attachment point to the exhaust elbow. I have pretty good diesel engine knowledge (I completely tore down and rebuilt a Yanmar 4JH2 TE a couple of years ago).

Two days before the incident I had made a 10-hour run under power from Princess Louisa Inlet to Pender Harbour (the wind blows straight in your face all the way down Jervis Inlet (a narrow fjord). The engine performed perfectly. I ran at 2100 rpm most of the way, but I did open it up to 2600 rpm for about 15 minutes. Again, no problems: temperature, oil pressure and alternator all nominal. No vibrations – just purred like a kitten.

The day before the incident, I installed a Renogy 20 amp DC-DC charger to use for charging the electric trolling motor I have in my dinghy. I used Ancor marine wire, 10-guage per the Renogy specs. I ran the wire to the main positive and negative bus bars located on the port side of the engine compartment. The wire run was about 5 feet to the Renogy. I used yellow heat-shrink ring terminals and plenty of zip ties to secure the wiring to existing wiring runs in the compartment. The Renogy checked out perfectly (these are nice units, btw).

On the morning of the incident, I did my usual checks: oil, coolant, v-belt tension. I dipped my fuel tank – 30 gallons. I did notice some water in the normally dry bilge. A visual inspection of the dripless shaft seal looked normal. I didn’t taste the bilge water to see if it was salt or fresh.

Before leaving my slip, I snugged the dinghy close to the stern. I started the engine (it starts instantly), checked for water out the exhaust, and backed out of my slip. I was motoring at 1000 rpm. When I was about 100 yards clear of the marina, I tried to throttle up to about 1500 rpm. The engine would not accelerate. No matter how much I opened the throttle, it stayed at 1000. I tried reverse. Again, no more than 1000 rpm. Then the engine began to lose power. I checked the exhaust at the stern – no water was coming out. Surprisingly, the temperature gauge remained normal! I made an immediate u-turn and headed back to an open space on the outer dock. I just barely made it. I shut off the engine and noticed black smoke coming from the engine compartment. I opened the access panel and smoke poured out. I grabbed my fire extinguisher and sprayed it liberally all over the engine compartment. I closed the access panel, and the smoke subsided. I opened the panel a few minutes later, and the smoke was slowly dissipating. I fitted a fan in the companionway to clear out the smoke and left it running for a day.

The next day I fully opened up the engine compartment. The Cheoy Lee has fabulous engine access, btw – best I have ever seen on a sailboat. I spent about a half day with a shop vac to remove most of the fire extinguisher powder. I followed this with another 2 or 3 hours with dampened clean shop rags and removed all traces of powder from the engine and everything else in the compartment.

I looked for signs of fire damage. There was NONE! I checked the new wiring run I had installed the previous day. Perfect condition. I checked every hose and cable. None showed any sign of damage or over-heating. The engine looked like it had been freshly installed. I checked the sea water pump impeller. Perfect, undamaged. I checked the sea water strainer – clean and free running. Then I checked the bilge. I had about three inches of water in it.

OK – that’s it for the background info. If you want any other info, let me know. When we’ve had a few guesses, I will reveal the cause, and how I found it out.

[AA3JY]

Engine sump oil level?

[LeighWebber]

Dipstick showed full. No sign of water in the oil.

[Bill O]

The "smoke" was steam and you had a water leak or you fried the alternator belt.

[Captbob47]

Dingy line around prop shaft?

[glenn.225]

Did you happen to notice an oder to the black smoke; burnt rubber, electrical, exhaust or anything else distinctive? Was the water salt or fresh?

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[glenn.225]

Originally Posted by Captbob47

Dingy line around prop shaft?

Could be this with the smoke coming from the carbon portion of the shaft seal.

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[Knotical]

Something with the shaft seal, water poured into the bilge rather than lubricate the seal.

[Tin Tin]

Raw water pump seized, pulley jammed and leaking water, V belt started smoking.
Alternatively maybe exhaust elbow hose popped off.

[LeighWebber]

Great suggestions. Comments below.

Bill O: the smoke was black, not white, so could not have been steam.

Captbob47 - I snugged the dinghy up close before departing. Afterwards, the dinghy was fine -- its tether was free.

glen.225 - The smoke smelled something like burnt rubber, but very toxic. My CO alarm was going, btw. It might have been diesel exhaust, but did hard to say because it was so thick and black. I don't have much experience with black diesel exhaust though.

glen.225 - the boat's in the water, so I couldn't dissassemble the shaft seal to see. From the outside, though, the seal looks perfect -- no discoloration. I did check it afterwards by turning the shaft coupling by hand. It turned easily and smoothly.

Knotical - that's certainly what I thought was bringing the water onboard. But it doesn't explain the smoke. Afterwards, the seal just sat there happily, no drips, turned freely.

[LeighWebber]

Hint: glen.225's idea about the smoke is on the right track. During the incident, my immediate fear was an engine room fire, in which case I had seconds to react or risk losing the boat completely. I opened the access panel, emptied the fire extinguisher, then closed it. The smoke was so bad I couldn't stay below to think much about it -- I had to get out to fresh air. All I could think of was burning insulation or burning rubber. But as you will soon see, there was no fire at all.

[IOM]

You backed into the dingy, blocked the exhaust outlet, which pushed the exhaust outlet pipe off, the water was from the raw water going into the bilge, hence no overheating, the black smoke was in essence over fueling because there was actually no oxygen to burn with all the fuel you added, and there was no oxygen because you were feeding exh gas into the air inlet in essence. 1000rpm was from no decent combustion, no oxygen = no power.

No damage done except a lot of mess

[Jim Cate]

Does the engine turn over normally, either by hand or with the starter? Does the v-belt look normal? Can you rotate the raw water pump by hand, belt off? Can you rotate the alternator by hand, belt off?

Jim

[chris mac]

I'm thinking your belt heated up and blew. Smoke was belt rubbing through, water was from pump being pulled off kilter a bit, then belt blew and water stopped flowing.
I'm thinking this mostly because that's what happened to me a few days ago. Luckily I could just shut that engine down as we are a catamaran. Limped along on the other engine while I aired out the engine bay and diagnosed it.
I'm also hoping that's what happened because it's a pretty easy/cheap fix for you.
The 1000 rpm has me a bit stumped though

[KingRichard]

Blocked or restricted exhaust