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Intermittent Overheating
Attention all you experts out there: here's my story:
I recently purchased a 1982 C&C 27 Mark IV with the original Atomic 4 engine. The boat is sailed in salt water. The compression is reasonably good and, after a few problems with stalling that a tune-up seems to have resolved, it starts and runs well. The engine was rebuilt in 1994, and has been freshwater cooled from that time.
However, after a couple of outings, the engine overheated badly, and we had to be towed back to harbour. The mechanics took the cooling system apart and replaced the exhaust riser (which was badly rusted), the fresh water pump and impeller. They also boiled out the heat exchanger.
Shortly after that, I took the boat out. It takes about 30-40 minutes for me to get out of the harbour, and the engine ran fine. It also ran fine getting me into the destination harbour. But on the way home, the engine was clearly overheating again. A mechanic came and worked on it for several hours, and it seemed to be running fine. The next day I left the harbour on my return voyage, and the engine worked fine, but on my approach to my home harbour, it overheated again. Again, the mechanic worked on the engine, and it seemed to run fine. On a subsequent sail, I ran it twice, about 40 minutes each time, and then the third time it overheated, and I had to call for help.
I have noticed three things that might be of some diagnostic importance. First, on startup, the engine exhaust spewed out a white plume of water with small white particles, which I am guessing is a result of salt buildup. Second, the water exiting the exhaust comes in very irregular spurts. You can hear it building up before it shoots out. Third, when I start the engine after a couple of successful runs, there is very little if any water exiting the exhaust; there is only or mostly steam, and the engine subsequently overheats.
Although the mechanics don't seem to consider it likely (and I am no mechanic), I think the problem is in the raw water cooling system. The inlet has been checked and is clear, but somewhere along the way there is insufficient flow, and the salt buildup from evaporating raw water is blocking the system.
So who's right here, and what should I do? I've spent a considerable chunk of change so far with unsatisfactory results.
Thanks.
Lee
I recently purchased a 1982 C&C 27 Mark IV with the original Atomic 4 engine. The boat is sailed in salt water. The compression is reasonably good and, after a few problems with stalling that a tune-up seems to have resolved, it starts and runs well. The engine was rebuilt in 1994, and has been freshwater cooled from that time.
However, after a couple of outings, the engine overheated badly, and we had to be towed back to harbour. The mechanics took the cooling system apart and replaced the exhaust riser (which was badly rusted), the fresh water pump and impeller. They also boiled out the heat exchanger.
Shortly after that, I took the boat out. It takes about 30-40 minutes for me to get out of the harbour, and the engine ran fine. It also ran fine getting me into the destination harbour. But on the way home, the engine was clearly overheating again. A mechanic came and worked on it for several hours, and it seemed to be running fine. The next day I left the harbour on my return voyage, and the engine worked fine, but on my approach to my home harbour, it overheated again. Again, the mechanic worked on the engine, and it seemed to run fine. On a subsequent sail, I ran it twice, about 40 minutes each time, and then the third time it overheated, and I had to call for help.
I have noticed three things that might be of some diagnostic importance. First, on startup, the engine exhaust spewed out a white plume of water with small white particles, which I am guessing is a result of salt buildup. Second, the water exiting the exhaust comes in very irregular spurts. You can hear it building up before it shoots out. Third, when I start the engine after a couple of successful runs, there is very little if any water exiting the exhaust; there is only or mostly steam, and the engine subsequently overheats.
Although the mechanics don't seem to consider it likely (and I am no mechanic), I think the problem is in the raw water cooling system. The inlet has been checked and is clear, but somewhere along the way there is insufficient flow, and the salt buildup from evaporating raw water is blocking the system.
So who's right here, and what should I do? I've spent a considerable chunk of change so far with unsatisfactory results.
Thanks.
Lee
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