That’s a special motor. Did gramps buy the motor when it was new? I’m not familiar with your powerhead but do have an LS-37 with the same lower unite. I don’t think you have a problem. You only have a piston pump trying to cool a 2 cylinder motor. They just can’t move the same amount of water an impeller can. The fact that the water is hot indicates its removing the heat from the cylinders. Cars use to have 160 degree thermostats in them. Today they’re over 200 degree. Although you can’t go back in time, you are having the same experience your grandfather did when running that motor. Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.
