27. I was coming back from a long trip with the engine on, when all of a sudden, the motor ran quieter. I quickly turned off the motor and raised the sails. I had to start the motor again when returning in the harbor, but it still was running poorly. Recently I checked it and found that it is only firing on 2 cylinders, but the plugs, plug wires and distrubutor all seem to be in good shape. Where do you think the problem lies?

Your symptoms are very consistent with a head gasket failure.

Two important questions are: What is the compression in the two failed cylinders, and are the failed cylinders side by side? Poor compression in two adjacent cylinders would tend to confirm a head gasket failure between those two cylinders.

If you do not have a compression gauge handy, you can simply hold your thumb over the two spark plug holes. If you can resist the compression by holding your thumb against the holes while someone cranks the engine over on the starter, a head gasket failure would be the likely cause. - Updated: November 4, 2003