Hi, I have a 1980 60hp Johnson. When I crank the engine it pumps water through the tell tale just fine at idle and at higher rpms. As it warms up it starts petering out some. It still pumps but it acts as if there is a partial obstruction. When engine is hot it will barely pump water out the tell tale and starts blowing steam at idle. It will pump more water through as I increase the rpms but not enough to cool it properly. I have replaced the impeller and the internal sleeves and gaskets in water pump. Like I said it pumps just fine when first cranked up then peters out once engine begins to warm up. If I raise the rpms it will pump more water, if I idle the engine it will slow down to a trickle with steam. Not sure if maybe thermostat is giving me a problem or not. I hope not as this engine is 32 yrs old and has seen its share of salt water. If I have to take the cylinder head cover off to change the thermostat I got a 50/50 chance at getting the bolts out without them breaking. The engine runs like a top, one of the best running engines like these I've ever owned. What do you think?
