Yanmar 2gm20F Overheating...

[peterstoops]

Symptoms are that it will run for awhile on low rpms without overheating; once revving higher, the alarm comes on.
Have had issues in the past and "burped" it to eliminate the problem, but it comes back again; I cannot find any leakage.
Have replaced the thermostat and temp. sending unit; no problems with seawater pump.
Other thoughts? Thanks!

[jkishel]

Raw water or fresh water cooling?

[Attikos]

Have you checked the mixing elbow and exhaust riser (if there is one) for blockage?

[djmarchand]

The mixing elbow on Yanmar GM engines is notorious for plugging with soot and fouling the sea water side and causing the problems you are seeing. Take it off and replace it. They have about a 1,000 hour life.


If that doesn't solve the problem then you probably have a fouled main heat exchanger. Take off the end cap (the one on the inlet from the raw water pump) and look for pieces of impellers or plugged tubes. Remove any pieces and rod any plugged tubes out with a brazing rod or a gun cleaning rod. Then circulate 50/50 Rydlime or Barnacle Buster through the heat exchanger to remove all of the fouling.


Other causes are a blocked hull strainer or internal strainer, worn raw water pump, or even a collapsed suction hose.


David

[Wotname]

Originally Posted by jkishel

Raw water or fresh water cooling?

FWIW, the F in the model designator signifies fresh water cooling. e.g. 2GM20 is raw water cooled and 2GM20F is fresh water cooled. This is common across the Yanmar range.

[sailorchic34]

Just a note that I have used a bicycle spoke to clean out the gunk from the discharge elbow once the bronze fitting is removed. Also check the bronze fitting as that can get gunked up too.