My 2QM20 Survived My Best Destructive Effort this Week!
Yes, the 2QM20 is a stout engine... over-engineered if its robust size and weight is any indication.
I put mine to an unintended test this past week.
Distracted from my usual routine by being at a guest berth and also receiving guests, I failed to open the seacock for the raw water side of the heat exchanger and I also failed to look over the side as I always do to verify water coming out with the exhaust. 10-15 minutes later, in the middle of a narrow channel with grounding depth on either side, we saw a faint hint of smoke in the cockpit. We shut down the engine immediately and as I was springing for the fire extinguisher to shove in the engine area cut-out, I smelled the odor of coolant. Took all of .5 seconds to realize my mistake. I could still hear the sound of coolant venting out of the heat exchanger radiator cap and expansion tank. My first reaction was relief that we weren't on fire! Fortunately, the mainsail had just been raised and the wind was very slight. It was just enough so that my brother and father were able to keep us sailing in the middle of the channel while I went down below to assess the damage. To get to the raw water pump impeller, the altenator must be slacked from the belt and the pump unbolted from the side of the engine. Then finally the impeller cover can be taken off. The impeller was in about a dozen pieces. I just hoped that a piece hadn't lodged somewhere to block the system. Good thing I read on this forum several years ago when I first got into sailing that keeping the previous impeller (if in OK shape) can be a lifesaver. Anyway, got the spare impeller in, and the pump and belt/alternator back in position. Took about 20 minutes from start to finish. I expected that the engine had cooled down enough so that I could add fresh water to the anti-freeze side of the coolant system. The engine started right away and raw water was flowing out with the exhaust. And I could see that anti-freeze was circulating through the contained side. It seemed ok enough to resume the afternoon plan with some sailing.
The next day, we needed to use the engine for four hours since there was no wind to get us home. All seems normal. I can detect no difference in performance, sound, or exhaust smoke/smell. The engine still runs cool. There are no signs of oil, water or fuel leakage from gasket interfaces. I checked the the rubber impeller in the anti-freeze side of the coolant system and it survived unscathed, so we didn't run totally dry there. I think that I dodged a bullet.
Now I know that my overheat alarm ain't working and got to figure out why. And figure out a more fail-safe procedure than my memory for opening the sea-cock.