Safe Operating Temps

[Paul Clarke]

Hi folks,

I'll introduce myself, as I am new here, though I have been lurking since April when I bought a 1972 C&C 27 sailboat with its original A-4. It's a pleasure to be able to read older threads to get an overall feel for a subject.

My concern involves heat.

During the delivery in the Spring with the PO and myself onboard, the engine ran flawlessly for 2 hours, then the revs began to undulate. We decided to stop at a nearby marina which had a gasoline mechanic on staff. The mechanic couldn't be sure, but thought it might be the coil. He replaced it, saying it could be that over time it heated up and that might account for the 2 hours of steady running then a drop in revs.

I was sufficiently concerned with the Atomic 4 that when I had the boat surveyed, I also paid to have a mechanical survey of the engine done. I was advised to pull the carb and send it out for an overhaul, which I did. Otherwise, the report on the engine was that it clearly had had owners who had maintained it, and properly looked after it, including newish alternator, fuel/water separator, etc.

A week ago I set out on our first family cruise, and ran into troubles: after running for 4.5 hours to cross Georgia Strait from Vancouver towards Vancouver Island, the engine revs dipped, regained, then 10 seconds later the engine quit altogether. No luck trying to restart. 10 minutes later we noticed the engine temp had soared to 190 F (from its usual 130 F running temp). Then there was a geyser of steam which erupted from the stb cockpit locker (which is open to the engine space). With no wind, we were lucky to get a tow from a good Samaritan to where I had access to a mechanic.

Two days and several hours of the mechanics time later, I had a new alternator belt, and yet another new coil.

That eruption? That was the coil getting so hot it burst its seal and sprayed its liquid. And that brings me to my question of heat.

Would an engine operating at 130 F generate enough heat to make a good ignition coil too hot to leave a finger on? I ask, because my mechanic said I should be able to touch it and not get burned when the engine was fully up to temperature. I can't touch the engine head, for example, without getting burned.

Here are some possibilities:

1) After the engine comes up to a stable temperature, the engine temp gauge in the cockpit reads approx 130 F. The temp gauge is not that old (less than 5 years by the looks of things), but I suppose it could be completely wrong in its indication.

2) The engine is fresh water cooled, and has a fancy valve that looks like it is adjustable to increase or decrease water flow. Perhaps too little flow is happening?

3) Perhaps the engine is running at a temp that is absolutely normal, and the temp gauge is working just fine, but the coil was defective. My mechanic asked if the one the PO and I had installed several months ago had an internal resistor in it. I didn't know, and the coil had little in the way of labeling, other than "Made in China". My mechanic said either we needed an ignition coil with an internal resistor, or we needed an inline resistor. He installed a good quality coil with an internal resistor in it. That leaves me wondering if the suspect coil just wasn't up to multiple hours of running?

So maybe the coil objects, and the engine shuts down. Therefore, no more cooling water is circulating. We go from cruising at 5 knots to stopped. Naturally the engine temp rises. Would that normally cause an ignition coil to "blow"? Is there a good reason why the coil is mounted less than an inch away from the source of a lot of heat radiating from the back of the engine head?

Finally, the mechanic sends me on my way. I'm wary, and nervous. The holiday is all but over, and there is no wind. I'm forced to motor for close to 18 nautical miles. I keep checking the coil, and during the first half hour or hour I *could* comfortably touch or even hold the coil, but after 2 or 3 hours of continuous running, the engine temp is up to about 145 F (slightly warmer than normal) and I could no longer hold my finger against the ignition coil. It was just too hot. I throttled back to about 4 knots as a compromise, and the engine temp gauge goes back to about 130 F.

I was very happy to reach that night's anchorage, I can tell you.

Too many issues are "new" to me... 35 years of sailing and motoring under my belt, but I am a raw recruit when it comes to this particular engine.

Any insights?

-Paul

C&C 27
Canvasback