Here are the areas I monitor at 3/4 to WOT for at least 3-5 mins continuous run time. If temperatures stay below 163°, I give the motor a green light. If they don’t, I dig deeper into the cooling system.

On motors below 6hp (say the 2, 3, 4, & 5), I only monitor the side cylinders as the heads and top of the powerhead usually go as high as 200-220°.

For newer motors (say, the 25/35hp 32cu. inch blocks, I just follow what the service manuals say for temperature checks [much more detailed explanations for service work in those manuals]).