99 Polaris SLTX-B question....

I just rebuilt a basket case engine for a friend. I have everything hooked back up and engien set back inside of hull....It was pretty easy and didn't take very long....But i have one item that I can not figure out where it goes....It appears to be the temp. switch sensor.....It is a round button with a spring under it and has a rubber grommett on it also.....I can not figure out where this goes.....according to parts diagram, it showed it being up around the water manifold or the thermostat housing.....There is no place for it to go anywhere around that location.....I am thinking maybe it goes in the ex. manifold somewhere on the bottom.....Not for sure...was not going to manifold back off without asking you guys first.....thanks to any who reply....It will be greatly appreciated.....tim