We had this same thing happen to us on our previous boat. It was caused by a faulty ignition key switch. It was the type of switch similar to a car, where you turned the key all the way to the right to the "start" position to start the engine, and when it started you released the key and a spring pulled it back to the "on" or "run" position. This internal spring failed, and the key stayed in the "start" positon meaning the starter remained engaged. We did not notice that the key had stayed in the "start" position and motored for over an hour in this condition with no problem - as long as the starter gear was engaged in the flywheel, the speed of the starter was regulated by the speed of the engine, there was minimal load on the starter so the starter really wasn't drawing much current. However, we approached a lock and tied to a dolphin to wait for the lock to open. We left the engine running at idle. My wife went below to heat some water in the microwave. When the microwave began drawing high current thru the inverter, the voltage on the starter solenoid dropped low enough that the starter gear disengaged from the flywheel. Now the starter was running full speed with no load. A minute later, it self destructed, burning all the insulation off the internal wiring. We smelled smoke, checked the engine room and immediatley turned off the battery switch (located outside the engine room). This prevented any additional damage to wiring. The starter was toast, and could not be repaired. To prevent this problem in the future, I replaced the key switch with a simple "on/off" type switch and installed a starter button in series with the switch. Ray B. m/v MOJO Bebe design #112 - Passagemaker 49-10 in steel > It looks like the starter had never disengaged, so it > continued to draw hundreds of amps; this much current > just completely fried our 1-2-Both battery select switch.