Overheat alarm

[Jason.mann48]

1996 Johnson 115 crossflow. 65 hours on new power head. Overheat alarm (steady tone) turns on and stays on after approx 5 minutes of motor running. I dropped the lower unit already, water pump looks brand new. Pulled the thermostats and tested them in hot water. They both opened at approx 170 degrees. Ran motor with thermostat cover off and water is flowing through block. Pulled temperature switches and tested them in hot oil. Received continuity from sensor to wire at approx 207 degrees. Now I'm stumped. Somebody please help.

 

[jakedaawg]

I guess at this point you pull heads and check diverter rubbers

 

[Jason.mann48]

I'm gonna be totally honest with you here. I have no idea what that is.

 

[jakedaawg]

They are pieces of what looks like rubber hose placed strategically between the sleeve and the casting to direct the flow of cooling water.

 

[ondarvr]

Try it with the thermostats out and see if the alarm comes on.

 

[emdsapmgr]

When you had the stat housing apart, did you check the hole in the nylon valve body? That model has a small oblong hole in the valve body plate, inside the thermostat housing. If that hole ever gets plugged with debris, both sides of the powerhead will overheat. That hole bleeds hot water to the back side of both of the stats, telling them to open. If it gets plugged, automatic overheat. The single hole on these later models replaces the dual small holes on the earlier crossflows. This one does not usually plug up, but it's worth checking. Agree, you may want to pull both heads and double check the placement of the rubber water diverters by each cyl. The can get out of position and can lead to overheating. The center diverter is correctly positioned, the one on the right is out of place. The picture would not post to this thread, see thread #7.

 

[emdsapmgr]

crossflow

 

[flyingscott]

Get a temp gun and see what he actual temps are and aren't you supposed to have 143 deg thermostats in that motor.

 

[emdsapmgr]

The factory thermostats are supposed to open at 143 degrees. The hot horn will signal when the engine heats up to around 212 degrees. The hot horn will cancel once the engine returns to 175 degrees-which is still considered way to hot for normal recreational use. That engine should vary between 143 and 155 degrees during normal operation. If your stats open at 170, they should be replaced with new ones.