The plug that wouldn't play

We've been chasing a problem with our starboard engine all season. Both engines would run fine until we had been running for several hours and then the starboard engine would stop. We could restart it but it wouldn't run above about 1,800 RPM. Next time out, the same thing would happen. Sometimes, (now that we look back on it) the engine would quit if we ran into some rough water.

We began with all the obvious stuff: Water separating fuel filters? Clean. Carb filter? Clean. Ignition system? Installed two new Mallory distributors and coils. We check the plugs and even changed the plug wires. What the hell was going on here.

This weekend, we tacked the more difficult things. We move the furniture in the salon so we could get at the hatch over the gas tank. We removed and blew through the gas tank vents. Nice and clear. We removed the pickup for the starboard engine from the tank. Looked like new, with no obstruction.

While we were down in the engine space, we decided to inspect the rubber plug that connects the engine to the boat's wiring system. We couldn't get the plug and jack assembly apart but it looked ok.  We jiggled it and decided to quit since it was getting dark.

That evening, we noticed that the salon lights didn't work. Neither did the courtesy lights on the cockpit. In fact, none of the boat's electrical accessories worked. We went to bed (in the dark) with the thought that we'd check this out in the morning.

Next morning, we made some preliminary checks of the electrical system behind the lower helm. Those accessory circuits had to have +12 VDC but we measured zero.  We went back the connector at the engine that we had tried to open the previous afternoon but this time, we used our 12-volt test light that has a pointed end you can use to penetrate the insulation to get a voltage reading. The connector has six terminals, five of which are for instruments such as temperature and oil pressure and one large (14-gauge) that supplies +12 volts to the two helm stations. Sure enough, there was +12 volts on the engine side of the connector but nothing on the 14-gauge wire on the other side of the plug.  We pried the connector apart and the big (14-gauge) contact dissolved into small bits of corrosion. We had the parts with us to bypass the connector and that's what we did. As soon as we put the jumper in place, all the boat's accessory circuits came on.

Time for a test ride. With John T aboard (old friend, master mechanic and someone who had told us to check those engine connectors), we drove down river at 3,000 RPM and back for a total of 19 miles. The starboard engine never missed a beat.

Here's a picture of that nasty connector that fouled up so much of our summer. We'll remove all of those connectors during the winter and wire them properly.