Need help replacing my thermostat

[Jon 1975]

Hello I’m new to this. I have a 1986 mercruiser 3.7 liter 170. Can anyone tell me how to get to the thermostat. I bought a new one and need to replace the old one due to overheating at mid to high speeds. Thanks for any guidance on this issue.

 

[Chris1956]

Generally the thermostat is under the cover, with the water hoses on top of the block.

Thermostats do fail often in I/O motors, but overheating can also be caused by the outdrive impeller wear, and clogged exhaust manifolds and risers.

 

[Faztbullet]

Biggest problem on those motors was heat exchanger and head gaskets..Closed system like auto

 

[Jon 1975]

[No message]

 

[Jon 1975]

I have found the thermostat in this diagram. Do you know if it is difficult to get to it?

 

[Faztbullet]

I bought a new one and need to replace the old one due to overheating at mid to high speeds.

This is not a t-stat problem...impeller weak or bad,heat exchanger has obstructions,anti freeze below 50/50 mix ratio or water tube or hose problem...