We have a 120 Mercruiser. The water temp guage is showing it is running hot 220 all the time.?

Question

We want to check the thermostat but I am not sure where it is located. Any ideas?

Answer 1

Maybe your intake is blocked.  Or you impeller is damaged (melted) from being operated when not in the water.  Squeeze your hoses and see how much water is passing through.  I never had problems with thermostats on my boats.  I don't even know where they were located!

If you ran the engine in your driveway without a hose and earmuffs, then you've melted/damaged your impeller.

Answer 2

both of the answers above are correct, you can just take the thermostat out and see if it overheats, also you can check the thermostat, by heating up water in a microwave and put the thermostat in it you Will see if the spring compresses and it opens up.get the water to about 160 or 180

Answer 3

earth your gauge wire out to make sure it's working correctly. what does it read when it's cold? pull the sender out and put it into boiling water to see if operates correctly. put the thermostat in the water also, it should open near boiling point.

Answer 4

Might be low on water or Anti-Freeze, Thermostat could be stuck, or it could just have a hot Thermostat installed in it, that is pretty common if you live up north, it gives you more heat.  The thermostat is located on front of the motor block where the water hose comes out of the motor and goes to the top of the radiator.  You can't check that but you could find it o,.k. if it will  help you any to know where it is.

Answer 5

What Bily said. Also, check to make sure that the cooling water intake is clear. It's easy to suck up a piece of plastic.

    Look for a hose that runs from a through-hull connection to the engine's water jacket (the outside of the engine or the heat exchanger)... it might run through a filter box first, but even so, that'll get you to the thermostat. When you disconnect the cooling water hose, you'll find the thermostat.

Answer 6

The stat should be located where the top hose comes out to the out side. Are you sure its running hot or could be a faulty switch or gauge? Is plenty of water coming out discharge pipe?

Answer 7

top front of the motor... housing contains the thermostat.. make sure the impeller is good in the outdrive .. is it pumping enough water to the motor...  The impeller in the outdrive lower unit pumps the water out of the lake to the engine.. it has rubber fingers on it that do the pumping.. if it isn't replaced regularly the rubber fingers get hard and brittle and can even break off.. causing you to not pump water at all.. Make sure it is in good shape.. They are not expensive and not that hard to put in.. I replace mine myself every other year..

if your running it off of earmuffs and a garden hose its not uncommon for the hose to not supply enough water to keep the engine cool...