Overheating

[Bassguy2]

I have a 1995 Mercury 150 XR-6 Serial # OG166883, the water impeller was changed on 2/07/2019. I have had the boat in the water well after that date
and hadn't had it in the water since. So, yesterday I hooked up the water muffs and cranked up the water and started the engine. Everything is fine but while waiting for the water to come out of the "pee hole" (for lack of a better term), the overheating alarm went off. I did shut it off and waited for the engine to cool. I was thinking
it could possibly be the thermostats. I pulled them both and found one did not open while the other did. So the question is, impeller or thermostat problem? The last time
I was at the lake it performed with no issues....Thanks for any replies in advance.

[leonreno]

If thermostat didn’t open then that definitely could have been the cause, but either test them or replace them. Need to make sure it’s the thermostat not opening and not the water not getting to that thermostat.

[Bassguy2]

If thermostat didn’t open then that definitely could have been the cause, but either test them or replace them. Need to make sure it’s the thermostat not opening and not the water not getting to that thermostat.

I tested both of them with water aprox 143° with a candy thermometer, well 150°....one opened and the other did not. While I was waiting for the water to come out the discharge pipe, I could feel little puffs of air which I could only assume it was the impeller pushing air out.

[leonreno]

Ok, definitely replace, and good chance that was the problem.

[EuropeanAM]

Definitely replace that thermostat- also need to see what your water pressure is.

Make sure ALL THREE gaskets are replaced when doing the water pump (notorious for torn gaskets below the impeller plate).

[Bassguy2]

Definitely replace that thermostat- also need to see what your water pressure is.

Make sure ALL THREE gaskets are replaced when doing the water pump (notorious for torn gaskets below the impeller plate).

The thermostats arrived today and I installed them. I tried running it again and alas no water coming from the discharge pipe.

[JOE54]

start at the source = pump and components

[Bassguy2]

start at the source = pump and components

I'm going to order the pump package tomorrow and go from there....what's the old saying? B.O.A.T, break out another thousand?

[JOE54]

DATS RIGHT

[lpugh]

Are you sure you had enough water volume thru the muffs? do you have a lower on it now that has water pickups in the nose cone?
Just checking since you said there was no problem the last time it was on the water
Be sure to check the cover carefully for damage from over torqueing the bolts and Use a Torque Wrench