does a I/O have a thermostat

[spareparts]

water pump impellers on mercs are an annual service item, don't forget to top off the gear lube when you're done. If the impeller checks out, and you replace the thermostat and it still overheats, sounds like you may need to check the manifolds and risers for blockages

[THEFERMANATOR]

And depending on which t-stat housing you have, it may need new check balls and springs.

[spareparts]

the check balls Ferm is talking about are inside the hoses that go to the risers, its in that T fitting in the top of the housing, if they aren't in there, or if the spring is gone, it will overheat

[UBHSTRY]

Originally Posted by spareparts

the check balls Ferm is talking about are inside the hoses that go to the risers, its in that T fitting in the top of the housing, if they aren't in there, or if the spring is gone, it will overheat

Wow really?? I did not know this. I thought they stopped water from flowing, not used to make it flow.....

[spareparts]

The check balls restrict the water flow so the block will stay full once the block is full of water the check balls allow the water to flow past ton the risers. It prevents steam pockets and promotes even cooling