Originally Posted by SawWhet
One item not mentioned is the engine thermostat? Had a similar tempeture swing on our last boat equiped with a Yanmar single cylinder Thermostat was worn and sticking
I am thinking that thermostat and housing is an area of interest as they say. I am amazed the yanmar thermostats actually work seeing they are really small, and seeing my engine sends raw sea water through it makes it even more amazing. I replaced the thermostat about two years ago and the stat and housing was full of white material- think it is calcium carbonate that precipatates out of sea water when heated.