Re: 70hp thermostat compatibilities?

[Don]

OK, well adding the big diameter overboard hose would lower the water pressure…This would not create the condition you are experiencing…And, the engine runs cool at high speed, so I would not worry about it.
You have the original style white thermotat assembly…I thought I remember that you could unthread these to get at the vernatherm. What style thermostat seat is in place? Like I say, I prefer the original style with the SS retainer over the "updated" hard rubber plastic seat that was pressed in without the retainer.
So, am guessing that the vernatherm is not seating properly inside the white thermostat assembly, or the thermostat seat is mismatched/messed up.. That fancy water pump kit included a replacement blow off spring for the original style thermostat as well, the best I remember. I don’t recall if the replacement spring was stiffer or weaker than the original though.
Will call you later, don’t want to confuse this situation further….
Adding the wide diameter overboard indicator would have lowered the water pressure slightly, so this would not cause the situation you are experiencing…