Overheated on season's maiden voyage

[Sailwood]

ASPEN (Columbia C29 #131) just splashed yesterday. The early model A4 was acid flushed on the hard, rebuilt raw water seacock, new hoses to the new Moyer pump, new thermostat, and once in the water checked for leaks and water from the exhaust. All ok. I motored from the yard to the slip. 3/4 way there the engine overheated big time. At slip a stepwise investigation ensued. I removed the tstat housing and found the stat fully open as one would expect, but absolutely no water inside. I then checked from the intake inward. Water comes in through intake, makes it to the T-fitting for flushes, makes it to the pump, exits pump when hand cranked, makes it to the T-fitting at the side plate, makes it to the tstat housing, and eventually makes it to the exhaust. Perplexed, I started the engine and everything was perfect for 30' when I shut her down and wondered what the problem was. I haven't a clue. I left the tstat out, but I doubt that was the problem anyway.

Is it possible that the acid flush caused something to flake off and obstruct the inflow? That doesn't make sense either as the t-fitting at the side plate would allow water to the crossover (late model head) and there was none there. Plastic bag idea over the intake strainer seems more plausible. Is it advisable to repeat the acid flush? There sure was alot of muck when I initially flushed it (1 gal muriatic to 5 gal water, let stand 15', then flushed afterward with 15 gal water.) A higher concentration?

What about heat damage to the engine? Noticed some oil (not alot) on top of the bilge water, nothing in the engine compartment. Ran great afterward without obvious abnormality.

Long post, I know, but am more than a little worried.

Doug

[Don Moyer]

Doug,

I'm not sure what caused your problem. Intermittent problems can bring us all to our knees because we're trying to fix something that is usually no longer broken. In your case, we're sort of left to speculate (as you're suggesting) that a piece of crud lodged somewhere in the system caused the overheat and then moved on.

In the area of long shots, sometimes a piece of broken impeller (from a failure, perhaps years ago) will get caught in the 90 degree elbow coming off the water pump and alternately flop one way or the other to stop and start the flow of water through the system. Or the lining on the inside of the rubber exhaust hose can separate from the rest of the hose within the first several feet behind the water lift muffler and wrinkle up to block the flow of water and exhaust. In both of these cases, the condition can clear itself for a while, and then return.

Best regards,

Don

[shemandr]

An overheat story

Now that my stalling problem is better, I had an overheat incident. After running the engine hard, going directly into a 25 to 30 Kt wind wind short steep waves, the engine shut off and the temp was 180 degrees plus. I have never seen the gauge over 120 and I actually didn't think it worked. I believe the engine ran out of gas and the stall was a coincidence. There hasn't been a sign of overheat since; but, I haven't driven the engine that hard since. The exhaust spills the same amount of water as always and even when it overheated I didn't notice any steam in the exhaust. I am speculating that the violent motion of the boat caused the water intake to suck air. Is this wishful thinking?

[Don Moyer]

I don't believe it's wishful thinking to speculate that your through-hull cavitated during your rough sea condition. We get several reports each year where a particular sequence of rocking and rolling in high seas causes an engine to overheat which displays no cooling system problems in more normal sea conditions.

Don