Johnson 55HP (Where's that cooling water Going)

[David Hills]

Can anyone explain how the cooling water is circulated in my Outboard? It's a 1979 Johnson 55HP 2 cylinder.<br /><br />The engine runs fine for approx 20 minutes then the pee hole stops showing flow and it starts to over heat.<br /><br />I just striped and rebuilt the water pump but it all looked hunky dory.<br /><br />The cooling water seems to have 2 return paths, one down the exhaust and one back into the lower housing. Is the flow through the head controlled via the thermostat? How long would it normally take for the thermostat to open and would it have been possible that it’s been put in backward, so when it get hot its cutting off the flow to the head instead of opening it.<br /><br />Is it safe to run the engine with the gear box removed and a hose pipe connected to the water intake pipe. If the thermostat is closed you could not flush the head passage ways with fresh water until the engine warms up.(is that correct)<br /><br />Many Thanks for any advise <br /><br />Dave

 

[dkondelik]

Re: Johnson 55HP (Where's that cooling water Going)

'afternoon Mr. Hills,<br /><br />to address one of your questions, do NOT start/run the motor with the lower unit removed. without the load of the L/U, the motor can race dangerously, resulting in major damage.<br /><br />is the thermostat old? sounds like it could be sticking. 20 minutes? sounds like a long time but could be a stuck thermostat.<br /><br />might want to pull the thermostat out and cook it in some water on the stove. use a thermometer to monitor water temp to confirm if/when it opens.<br /><br />letus know what you find<br /><br />Good Luck