I have a Westerbeke 9.0 BGB generator on our 1990 390 EC that has been giving me fits the last two seasons. Problem: Starts fine and runs for some undetermined amount of time, sometimes 20 minutes, sometimes an hour. After a while of running (both under load and without load), the gennie shuts down. Acts like it ran out of fuel kind of sputtering to a stall. This past winter I replaced the impeller, plugs, cap, rotor, and wires, fresh oil change and filter. The coolant level is good. I found some time to work on it this weekend after reading a post about the fuel solenoid in line just after the filter. Jumped out that solenoid and no change. What I did notice was the time the gennie ran before shutting off was very short the last two times I have run it. Probably 10 - 15 minutes max. After the gen set shuts down, it will start right back up, but shuts off very quickly. I believe that the motor is getting over temp and shutting itself off. I checked the water coming from the exhaust on one of the restart cycles and that water was quite cool. I expected it to be much warmer. The coolant temp in the gen set does get quite hot, but not sure exactly how hot. So, I guessing it is time to service the heat exchanger? Has anyone done this before and exactly what is the procedure? If you have other advise as to what might be happening, I would be appreciative to hear it. Thanks in advance.