Thermostat on Chris Craft B?

[ventport]

A friend of mine has a Chris Craft Herculese B engine is his boat. The engine has just been rebuilt and we cannot get the engine up to temperature. The water pump is working correctly but the head is just warm to the touch and it will not even register on the gage. We have checked the sending unite and it works the gage, so we know the engine is not up to temp. Is there a thermostat somewhere on this engine?