Breaking 50! Need new thermostat?

Just wanted to say how stoked I am. I got the boat out this past weekend and I can break the 50mph barrier (barely). I got the interior put back together and carpet in place just in time for the weekend. Speedos are finally working due to the new pickups, and my new tach is working great.
I will post some picks of the interior when I get some time...

Only immediate thing that needs some attention is most likely a new thermostat? The temp stayed at 120 when operating. After I stopped running and put the boat in the lift then the temp would go up to 135. I am guessing that the thermostat is stuck open/ partly open.

Does this make sense? Gauge obviously works, temp stayed cool when running -- means water is cooling properly when running, manifolds were at right temp (warm -not hot), and temp went up when not running (when water was not actively cooling). These symptoms point to a open thermostat???

I will probably pull the termostat and check it out.

You can verify the sender with a pot of hot water. Just put the sender and a thermometer into the hot water for a quick check.

Sometimes a small piece of trash can lodge in the thermostat and it will stick open. Many times you can pull the 'stat and get the trash out and it will work fine.

My boat has a 145 'stat and runs around 140.

Matt