It seems to me like some had the thermostats and some didn't. If it has one, there will be an obvious gizmo with a spring device, to hold it in, near the top of the power head. If it has a thermostat, they were very prone to plugging up with corrosion, in that area. Either way, there IS a peep hole, or tell tale. I want to say it's on the starboard side of the lower cover but I can't remember. Maybe port. It will have a 1/4" black hose coming from the top of the power head, or the thermostat housing. If you have a thermal sensing gun, it shouldn't get any warmer than 160, even with a thermostat. If you don't have a gun, run the engine and put a few drops of water on top of the power head. If it boils, stop; you have a problem.
With these engines, it is not easy to MISS the water tube going into the pump; but it is very easy to BEND the water tube, so that it will not go completely INTO the grommet on the pump. But let's see if you are actually over heating or not.