Where to go next?

[Fred]

I'm having a very frustrating experience with my engine. Starts like a charm, runs at lower RPM and cooler (120 F not 140 F) than it did and for some reason after running the engine for a long period of time, it gently stalls. If I wait for a couple of minutes, the engine starts again.

I have tuned the engine up, plugs, points, distributor cap, rotor, condensor and spark plug leads, all set to TDC.

Topped up with fresh fuel and have added Marvel Mystery Oil to the fuel and run the engine, grant it not for several hours but fors some time.

All cylinders have compression in the 90 psi range, but the number 3 cylinder is at about 80 psi (tested cold).

Is it possible that it's the coil? It has not been touched since I have owned the boat, about 12 years. It gets hot when run for about 15 minutes, but there is no rust or oil leaking from it, is it worth replacing the coil?

It feels as thought the number 3 cylinder is not firing, and when I remove the spark plug wire there is little change, but when I hold the wire to the top of the number 3 plug, the engine reacts as though it's about to fire that cylinder.

I have not looked at the fuel systems yet, is that a possibility?

Am I looking in the right places?

Fred

[jkenan]

I had the same experience with my engine, shutting down softly after running fine for an hour, and then a few minutes later being able to start it back up. With the help of Don Moyer, we realized my shutdowns were due to the coil because I had been keeping the engine cover off the engine thinking it was an oxygen issue, and never had a shutdown with the cover off. The engine ran cooler, and the coil never got hot enough to short out (the broken down insulation inside an old coil allows an electrical short when it gets hot, causing the shutddown).

I put the flamethrower coil on, and with the cover on providing the same ventilation, I have not had a shutdown since. A pretty easy and inexpensive fix if you ask me.

Good luck.

John

[Fred]

Thanks John,

Sounds like a similar problem and I should have a spare coil regardless. I'll let you know if it works!

Thanks again.
Fred

[Fred]

Hi Don and John,

Well after going back and looking at all of the ignition and tune up components with no found errors, the next step was look at the fuel service situation. We rechecked compression, on the now warm engine, and came up with 120 psi across the board.

Fortunately, a friend is very familiar with the Atomic 4 Zenith carb. While the engine was running, very roughly, Stew found the Idle Needle Valve was cranked down tight, so when it was released, the engine spewed out a mass of carbon black smoke and came to life. It runs at 140 degrees, runs smoothly and has a minimal amount of smoke coming from the exhaust.

Now the next question is, to rebuild the carb or not. It's a mystery to me as to how that little screw tightened down, so will a rebuild help? I know, I'm asking you how long is a sting, but better to ask.

If it is time to rebuild the carb, the flame arrester has Zenith imprinted in the side, does that make it a Zenith carb, or are they interchangable? The boat is a 1973 C&C 27 Mk II, if that helps.

Your thoughts?

Fred

[Don Moyer]

Fred,

In the face of your otherwise good performance, I wouldn't recommend messing with the carburetor at this time.

Don

[Fred]

Thanks Don.

Point taken, have a great weekend.

Fred