Over heating

[cusoak]

I have a 1995 90 hp johnston motor that the heat alarm goes off.
At first when I fired it up and ran it some the alarm went off.
It was puttin out waster through the pee hole.
Found that the left cylinder was hotter than the right one( standing at the back of the motor
So I pulled the thermostat housing off and found that the left thermostat looked bad and stuck ,so I replaced it.
It was also time to rebuild the water pump.
So instead of rebuilding I bought a new water pump assembly and installed it.
Then fired up the motor and still the alarm went off. Now both heads get hot and the little rubber hoses at the thermostat housing also get hot and soft.
What have I done wrong or what can be the problem.
The old impeller did not look allthat bad.
Need help.
Jeff

 

[SparkieBoat]

Did you install the new water pump impeller correctly? are you getting water from your tell tell? you may need to flush your motor, drop the gearcase and connect a water hose to the water pipe that goes up into your head, remove your thermostat housings and thermostats, turn hose on. flush. then put it all back together correctly. make sure the thermostats are in correct and make sure your pipe fits into your pump.

 

[cusoak]

I replaced the whole pump assembly. Instead of just the impeller. water comes the pee hole. with good stream.
Where can I find a water schematic that shows how the water flowes through a 90hp johnston

 

[SparkieBoat]

google it, lots of images for that.

 

[Faztbullet]

The "P" indicator just tells you impeller is working it tells you nothing about cooling..sounds like the t-stats have a problem.

 

[emdsapmgr]

The telltale only tells you that the impeller is pumping. It does not indicate that the water is flowing through the block. Water has to pass through the stat housing as it leaves the block. If there is a problem (blockage or malfunctioning stat) with either stat or the two pressure relief valves, one side (or both) of the block can overheat.

 

[cusoak]

how do I tell what is wrong with either item. thermostats or relief valves.

 

[SparkieBoat]

boil the tstats in a pot they should pop open at about 140-150 I think that is the right temp. put a thermometer in the water and see when they pop open. the relief valves should just be clean and not stuck or disfigured.

 

[toddschubert]

that motor has rubber "water deflectors" in the water jacket. You have to remove heads and replace them.they flatten and block flow in time. Cost about $60 for the deflector tubes and gaskets.As long as you are comfortable removing the head covers.

 

[emdsapmgr]

Johnson made two distinctly different 90 hp engines that year. Maybe you can post which model you have. The 90 degree crossflow or the newer 60-degree looper type. Helps us to know what you are trying to fix. Their cooling systems are very different.