Varying RPM, bad governor?

[s/vAngel]

Hello there again. Has anyone ever had to tinker with their inboard diesel's governor? I'm wondering because I have no idea what other part in my engine to place the blame... Last year, when crossing the Gulf Stream, the wind died and I motored. After a few hours, Angel's elderly 3-cyl, 20hp Perkins suddenly started "hunting", its RPM jumping up and down. I eased the throttle and it put her in neutral and it stopped hunting. I throttled back up and seemed to hit a flat spot where she'd hunt and then past that flat spot, it ran fine again. After that incident, once and a while, her RPM will hunt around for a moment or the engine, near the governor's location, will make a brief rattling sound.
Everything else seems to check out, can't find air leak in fuel, just changed the water pump">raw water pump and oil. filters are clean. Fuel, though from a foreign ports, is clean. all cylinders seem to be firing okay and sound well. Powers up okay, but with that flat spot. exhaust is a bit stinky (the foreign fuel?) and slightly white smoke at higher speeds. I've met two other cruisers who have Perkins and had to repair their governors, but I'm not expert enough to diagnose this personally. I know that I do have a mechanical type gov. with that whirlygig thinghy and a spring. There's probably a doo-dad in there as well. Am I missing some other problem or should I just dig in and change the sucker? Better yet, call in an expert!
Thanks in advance for any input. It's mystery motor theater, 2007.
Rebecca

[Alan Wheeler]

Sounds like the IP govoner. It's not something you can easily do yourself. The pump needs to be pulled and sent away for a repair.

[Sunspot Baby]

There are other possible causes. Even if the governor is trying to maintain a steady RPM, if there is trouble with the fuel supply, it is fighting a losing battle. Lift pump, injector pump(s), fuel line, etc. can exhibit intermittent problems. IMHO the first thing to do every time is have the injectors checked. From there, check that you have correct pressure or vacuum at each stage of the system before you tear into the governor.

George