Runaway Diesel.. or not?
I have a Perkins 4.108 diesel aux. engine in my 44' cutter. I've noticed that after periods of extended running, the engine will begin to surge slightly. At first it will surge from 2100 RPM to around 2400 RPM, and come back down to 2100. Gradually, over a few hours, this "surge and return" routine will work its way ever further upwards. I can pull back on the throttle to keep it running normally for a while, but ultimately the RPMs get so high that even pulling back all the way on the throttle won't bring it down. At that point, I am forced to also slightly engage the kill lever to choke off additional fuel. In this configuration, I can keep the engine running smoothly indefinately. Once I kill the engine and let it cool off, it resumes normal operation.
I've looked at the idle and stall preventer settings. They seem fine and indeed the engine will run for hours and hours before starting this. I've heard of runaway diesels before, but I'm not sure this qualifies. My oil and filters seem fine and I change them often. The engine runs very smooth, is easy to start, and doesn't emit any smoke. Could this be a problem with the injector pump?