Port Engine Goes Beserk!

[Xenophon1]

I have a 2004 Lagoon PC with twin Yanmar 315 hp diesels controlled by a Mathers Microcommander 463-4. When docking or maneuvering slowly (but not when running at speed) at low engine revs, usually going both forward and reverse, the port engine will suddenly rev up to full speed! Using the shift lever does not slow the engine; I am only able to stop the engine by pushing the button to put the engine in neutral. There are two control stations--one on the flybridge and the other in the main cabin--I've never had a problem with the controls in the cabin, but I am always on the flybridge when docking, etc. Needless to say, this is quite "unsettling"--I've had a few close calls but nothing more than a rough bumping of a dock so far. I called Mather, and they suggested checking the control arm. I did this, and found that the throttle plate was sticky. After a little WD 40, it appeared that the problem was resolved. Unfortunately, after about 2 weeks, the problem reappeared and no amount of lubing of the control arm and throttle plate seems to help. Unfortunately, this is an intermittent problem, and I'm afraid that the engine will behave when I put the boat in the water in two weeks, only to misbehave later this summer as I try to dock next to some mega-yacht! Thanks for any thoughts on how to solve this problem!

[boatbod]

If it only does it at one steering station, it sounds like a bad potentiometer in the control head.