1998 Mercury Force 9.9 2 stroke thermostat

[Jimheal]

I have spent a ton of time online looking for info on this. All pics and videos show a small plate covering the thermostat near the plugs on back of engine. Don't have that. My pee tube comes out of a large plate just forward of the plugs/head and the plate is mounted with 12 bolts. The only 3 bolt plate is behind the fuel pump on the engine opposite side from the pee tube connection. Anyone have any ideas on this? Am I looking at it already? Thanks.

 

[sdowney717]

Clearly shows it, and same for many years
Did someone modify your motor?

I have wondered if this thermostat is the same size as the ones used in the ONAN MCCK generator?
Cause every time I see one, it looks to be, and I doubt they are available anymore.

Thermostat Replacement For Mercury 2-stroke 6.0 8.0 9.9 15 HP 1986-2006 Martin Marine Episode 1

 

[Jimheal]

Well, apparently the "force" part of the description is the key. Instead of putting the thermostat up on the engine (like in that video and many others), they mounted it on the rear, well below the engine. They added a plastic block (1.5 X 2 inches) over it to hold it in place. Same as the Gamefisher model. Found it, corrected the problem. Engine now cooling as designed. Thanks

 

[tristanstanley58]

Those Mercs definitely had different setups across production runs. The pee tube coming off that 12-bolt plate means that's your cooling system — pretty sure you're already looking at the right thing.

 

[HelmutSheina]

These engines were developed from old Chrysler outboards, so you might find some help in that direction in future. It has vastly more in common with Chrysler than Mercury. Force Outboards: The Budget Motor That Divided a Generation https://powerboat.news/force-outboards-the-budget-motor-that-divided-a-generation/

 

[HelmutSheina]

Clearly shows it, and same for many years
Did someone modify your motor?

I have wondered if this thermostat is the same size as the ones used in the ONAN MCCK generator?
Cause every time I see one, it looks to be, and I doubt they are available anymore.

Thermostat Replacement For Mercury 2-stroke 6.0 8.0 9.9 15 HP 1986-2006 Martin Marine Episode 1

That one is for a Mercury designed and manufactured engine. The Force (or Mercury Force) are old Chryslers given a new lease of life with a rebadge, a colour change and a few Mercury bits.