PROBLEM WITH MY 1968 johnson 20 hp OVERHEATING???

[ajp1977]

Whats up guys! With this year of motor I know they didn't have a tell tale pee hole. I know it has a hole that sputters water from time to time but nothing like a traditional overflow stream of water. This is a new motor to me and I started it yesterday and no sputter of water and the motor got HOT!..I shut it down ASAP!...My question is if I take water pump housing apart and replace impellar and the motor still gets hot, what else could it be. Hoping that its just the impellar! THANKS

 

[eavega]

The cooling system on those motors are fairly simple; water pump in LU through the copper tube, through the thermostat and into the cooling passages around the cylinders, then out the exhaust. If the motor is overheating, look first to the impeller (replace), and water tube (properly aligned, no blockages). Next make sure that the thermostat is functional (put it in a pot of water @ 150 degrees, make sure it opens up, then closes up again when the water cools or when removed from the hot water). After that, you can connect a hose to the copper tube and make sure you are getting water flow through the passages and out the exhaust.

If you look around iboats, there is a procedure for adding a telltale to your motor. Its fairly easy and not expensive.

Good luck

-E

 

[ajp1977]

ok thanks eavega! I will have the lower unit apart in a little bit. I did research plans on how to install a telltale hole. your right it isn't bad. Never thought about checking the stat like that. I will let you know how it goes in a couple of hours! thanks again! Gotta have this problem fixed before this weekend!

 

[F_R]

There is a plastic water restrictor in the water outlet of that motor. Part number 313435. If the motor overheats, the restrictor melts into a glob of plastic, blocking the outlet. You have to remove the powerhead to get to it. You will also need a new powerhead gasket.