Any diesel diagnosticians out there? On our way down the Jersey coast, motoring in light northerly wind, the Westerbeke 40 began to surge. That is the RPMs increase by about 500 then returned to the original cruising RPMs (2200) and kept cycling like this. This started after about 7-8 hours of running. I shut down and sailed for about an hour, then started the engine again and finished the last 10 miles into Cape May with no problems.
The next day we had the same problem in the C&D canal after about 4 hours running. No sail option here so we brought back the RPMs to 2000 and the surging stopped. I did take it out of gear to see if it surged when there was no load, but this was not a fair test since I observed that if you crank back the throttle to idle then bring it back to speed the surging stops and doesn?t reappear for a few minutes.
The following day was another windless day we motored for 7 hours, but this time at only 2000 RPM. The surging did not happen again.
Now those are the symptoms, can anyone venture a guess as to the cause. Things I have thought of: 1. Hurth clutch slipping after it gets hot, 2. injector pump malfunctioning after same.