Grasshopper 325 overheating

[ILENGINE]

Grasshopper 325 with the WG750 Kubota gas engine. Showing in the red when running, tried new temp sensor and that sensor reads higher than the old one. wireless thermometer is showing 160-170 degrees at the top of the radiator. I am suspecting coolant flow issue but coolant appears to move through the radiator, Top of radiator shows 160-170 but bottom will be around 100 but will eventually get hot enough at the bottom that you cannot hold your hand on it.

So I am trying to decide if I have a thermostat issue or a partially clogged radiator, or is the water pump failing.

 

[Scrubcadet10]

take the t-stat out and put in water on the stove and see if it's operating properly and at what temps it's opening.