Re: Is it OK to leave thermostats out in warm climate (s. LA) on Jhonson 88 Spl 1993
This explains it pretty good.
The thermostat of an outboard plays a very crucial role in warming the engine to a satisfactory operating temperature. If an outboard is operated without a thermostat installed, it will surely suffer in some way from poor performance all the way to causing internal damage. An outboard is designed to operate at specific engine temperatures, and if it does not obtain that temperature, it will run very sluggishly, and also cause fuel/oil mixture to not totally burn, which causes excessive carbon buildup. Carbon buildup in an outboard is one of its worst enemies. This condition usually most often causes problems with the piston rings becoming stuck in the piston ring grooves. If this happens, you can pretty well kiss your powerhead goodbye, because it most certainly will allow the piston to touch the cylinder wall, and immediate scoring will result. Once a piston/s is scored, it is only a matter of time before the engine will self destruct unless it is caught in time to perform an overhaul.
