T-stat change in 2001 75 horse elpto?

[2004 Voyager]

Boat motor runs ice cold, I can touch any part of the motor after running at high idle on the muffs for thirty minutes. Seems the t-stat must be stuck wide open. Looks like there is a housing on the back of the motor, kinda up high and on the left side of the spark plugs. is this the t-stat housing? Just pull the few bolts holding this housing on, and replace the stat? Any and all advice appreciated, thanks, Larry