Guys I looked for anything like this and could not find so if I am duplicating I am sorry. I have a 15 KW Westerbeke in my 55 Sedan. It will start fine and run fine for around an hour loaded up light load etc does exactly what it is suppose to do. The nall of a sudden it will drop some RPM's and instead of putting out 230 it drops to 180 or less depending on the load. Completely unload it and the RPM's go back up and volts to 230. Load it and they drop. I have had a Westerbeke guy out and he said the back end is 100% ok but that is all he works on is the back ends governor functions as it is suppose to it is just an RPM loss. By any miracle has some one had the same issue I understand there is a speed sensor that might be the culprit. ? Thanks for any help.