overheating T50/TLR 50hp 4 stroke 2006

[Stephena]

Replaced water pump, full kit. Replaced Thermostat and cleaned sensor.
Motor pees ok in normal neutral. Motor pees better in faster neutral.
(sensor/alarm does not go off)

Place engine in gear and within a few seconds peeing stops and sensor/alarm sounds.

PLEASE HELP

WHAT IS WRONG?

ALL ADVISE IS APPRECIATED...

 

[deepsea21]

Is it doing this with the boat and engine in the water, the engine in a trash can filled with water, or the engine dry and hooked up to ear muffs and a garden hose?