The high heat alarm has started going off at high revs on my 1995 Mariner 60hp 2 stroke. The impeller is only a year old and there is a very strong tell tale. I'm thinking the thermostat might be sticking. According to the parts diagrams, there are two types of thermostat - 120deg and 143 deg. Anyone know which one is used on which model? My serial# is OG196273.