06-15-2011
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Member
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Join Date: Jun 2010
Location: Michigan
Posts: 64
Rep Power: 2
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Engine stall
Yanmar 3QM30H.
It’s a bit of a long story, so I thought I’d at least make it entertaining.
Two weeks ago we head out for a Wednesday evening race. The winds are howling 20kts gusting to 30 says the marine forecast. 10 minutes before our class start we raise the already reefed main. Between the gusts and shifting winds, we manage to blow out the main…shredded it, is a more appropriate choice of words…no great loss, it had long ago needed replacing.
By the time we left the slip, got to the start, blew the main and returned to the marina, we had been motoring for about 45 minutes to an hour. Now getting a boat back in her slip in a 20 kt crosswind is challenge enough, but to have the engine stall when you drop it in neutral added an element of surprise I am loath to repeat. Fortunately, the engine fired right back up again, both times it stalled, but not quick enough to prevent the crew and I from performing a couple of Benny Hill routines for the morbidly curious group of onlookers gathered on shore.
I’ve gotten into the habit of letting the engine idle for a few minutes to cool down while we tie up, and before shutting her down I take a quick look at the exhaust and the temp gauge. That day the exhaust looked normal: no steam, no white smoke, no black smoke, water pumping out like it should, but the temp gauge was pegged (the gauge is mounted about knee level and hard to see even while sitting down). I popped the hatch, and a quick look at the engine reveled nothing abnormal, like coolant spewing from the overflow.
Since tinkering with a hot engine while heeling over 30 degrees…TIED UP IN THE SLIP…wasn’t on my list of fun things to do, I thought it best left for another day, especially since we were going to be tied up a while waiting for a new main.
The weekend found my helmsman up the mast retrieving the halyard, replacing light bulbs and performing a little maintenance on the truck, while I dug into the engine. (Poor guy, seems the liquid courage we fed him didn’t agree, a few bottles of water and a can of Coke saw him through the rest of the project, he even had enough energy to remove the remains of his lunch from the hull afterwards.)
Of the many things I did to winterize/summarize the boat, it occurred to me that one thing I neglected to take care of was the air filter. Thinking it may have been starved for air, I gave the filter a look. It was quite apparent the previous owner had neglected that little chore, too, for several years. Many things could have resulted from that air filter, but starving the engine wasn’t one of them. Half of the foam was missing, what was left would crumble at the slightest touch.
Along with the filter, I ordered a new thermostat and temp sending unit. The T-stat in case the engine may actually have been running hot and therefore causing it to stall at low RPM, the sending unit in case the gauge is lying to me. The only other reason for a hot engine I can think of is air in the system, though there are no signs of leaks and I don’t know how air would have gotten in there. The coolant itself tested fine for boil/freeze temps.
I’m going to spend the weekend on the boat and be away from the net. I figure on replacing the t-stat (just because) and air filter, checking for coolant flow, running the engine up to temp and see what happens. I’ll monitor the output of the temp sender while she’s warming up and replace if necessary.
What I need to know is if there is anything I’m missing that should be looked at. Also, what would be a good method to burp the cooling system if there is air in there, and how would I tell if there is air in the system in the first place?
A couple of key points:
The engine stalled only when going from about 1500 RPM to idle, once started again it would idle smoothly.
I have both a heat exchanger and a potable water heater (coolant cycled through it to heat the water, you know the kind.)
Thanks in advance.
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