... way to deal with the issue! I have no problems at all when I give the heat exchanger a cleaning in the spring so this is what I have been doing. If I had continuing issues I would certainly look into additional heat changer capacity, it is a good idea.
One of my gripes with Yanmar is that they specified such an obviously marginal part for this engine. I have found other examples of "penny pinching" that are really annoying and simply not necessary, IMHO. Enough that I am not sure I would willingly consider a Yanmar again. It is too bad really as the basic engine is a very nice running little thing.
So it goes...
Bruce