1993 Johnson Thermostat Issue

[Wide_N]

I have a friend who has a 1993 Johnson 150 ELETR. It built up so much water pressure that it popped the thermostat cover completely off. Have you guys ever heard of anything like that? Compression also dropped to 40 pounds on the top two cylinders on that side. I am have my fingers crossed that it is just the o rings. Any words of advice before I dig in?

 

[emdsapmgr]

The powerhead may have gotten really hot. Typical that the top two cyls are the hottest. When the powerhead gets hot, some of the aluminum components start to change dimensionally and that can affect the clamp load on gaskets (and their ability to seal properly.) When you get into it, make sure your components you are looking at are flat. (the head faces, for one.)