It is not on the throttle body / manifold but it is on the same side of the head as the TPS ie Left if you face the rear of the boat. I have a great photo but the site does not seem to be uploading photos so I will try to explain.
On the left of the motor, it is installed verticaly downward from the top of the head. It is in the area behind the water pump / under the electronic gear/ to the right of the oil filler cap and slightly ahead of it. It has 2 wires to it White and Black which end in a black clip that clips onto the sensor.
You will use a LOT of fuel if this is faulty. I was running 2 to 3 tanks a day untill I fixed the issue ( multiple issues ). My boat looked like a diesel... and yes 2 families sking hard, at least 2 tanks a day so it was a priority to find the fault
If you want to test the OHMS resistance there is a thread of mine called "temp sensor resistance" (I think) that compares the resistance of my old unit / new unit and the factory spec.