Thermostat on Force 9.9

[Joe Morrison]

Hello

I have a Force (Mercury) 9.9 Outboard and I am not all that knowledgeable when it comes to outboards.

On the back of the motor there is a rubber housing covering a thermostat. The rubber housing has an outlet for water and there are two other outlets in the metal casing lower down.

What I am wondering is: what is the function of this thermostat?

If it is not working, what could be the consequences?

What would be the consequences of simply removing it?

I have been using the motor for very short trips to a moored boat. I am in the process of swapping it over to become the auxiliary on a power boat where it may be used for longer trips and trolling so I'm keen to ensure it is working properly.

Thanks for any tips shared.

Joe

[CDK]

There is some sort of plenum on which the thermostat is mounted.
Water, pumped up by the impeller pump on top of the lower gear housing is returning without circulating through the engine as long as the thermostat is closed. 95% returns internally to cool the exhaust, the rest goes outside through the "pee hole" to show that the cooling pump works.
Only when the thermostat opens, the water can enter the plenum and cool the engine.