Home › Forum › Ask A Member › running without a t-stat › Re: running without a t-stat
Thermostats on outboards [and stern drive engines for that matter] are one of the most neglected parts of the cooling system. I’ve seen more ”stuck open” T stats, vs. ”stuck closed” but either can happen. This summer I bought a 1988 Merc 25 tiller. After the usual carb work and a new impeller, it ran pretty good. Still, it always seemed a little lean at idle speed. Turns out, someone had removed the thermostat, and was running it without one! After a new T stat and grommet, it made a remarkable improvement in idle quality, and overall running. That engine could never really warm up, because of to much water flow. Thermostats should really be checked or replaced, when servicing the impeller.