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1963 Evinrude 18hp overheating

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I seem to have a water flow issue with my 18hp fasttwin. New impeller, checked twice. New thermostat. I have warm water out the exhaust port. Not sure whats going on as it is still overheating. Any help appreciated, Thanks
 
Run it in a barrel with a jug of saltaway in the water at least 5 inches above the cavitation plate. Run it at least 1/2 an hour and keep checking the head temp by putting your hand on it and count slow to six. If you cant hold your hand there it is overheating. If it stays cool the thermostat is stuck oem. Never run it above high idle speed in neutral.
 
The head temp is so hot you can't touch it. Seems to be a lot of pressure around the thermostat cover and exhaust cover. Pickup tube seems to be solidly in place but will check it again. Is there a pressure release valve? Thanks
 
I've owned the motor for a little over a year. Ran great except for water in the gear oil. Did a complete reseal of the lower unit which cured the problem. Now have the overheat issue. Where does the water go after it leaves the pick up tube? I'll try the thermostat trick in the mean time. Thanks
 
I've got a '65 Johnson 18 that exhibits the same problem. Seems to idle fine in a barrel but you can't keep your hand on the side of the head for more than a 3-4 count. Water is flowing out the exhaust with a great deal of steam and very little smoke. Thinking a tear down is in order for this one. Interested to learn what you find with yours.
 
The water goes directly into the water jacket in the powerhead then goes in two directions. On the side of the engine it goes directly between the two exhaust covers and straight out the exhaust and through the thermostat into the head and out the exhaust. The exhaust cover should only get warm as water flows free through it. If it stays cool and the head gets hot you have restriction in the thermostat or head. If the exhaust cover gets hot water is not going through the cover properly. Either way it is because the engine has mot been flushed properly. After each use put the engine in a barrel of water and run it until the thermostat opens usually three or four minutes then disconnect the fuel line and let it run out of fuel. Your all set for the next outing.
 
I had the same problem on my 1964 18hp evinrude,the problem was the head gasket.Apparently,the water pump and impeller can be working,but a blown head gasket interupts the water flow.I got a reduced flow out of the water exit on the leg,and steam.
I was advised on here to also change the exhaust water jacket gaskets as they can leak water into the cylinders and damage the bearings.
My stat was jammed open(because of the overheating)I am replacing that as well as the head gasket.
I put new coils/points/condensors and spark plugs,plus a carb kit and stripped and cleaned the carb with carb cleaner.
The motor was running like new.Unfortunately,the one thing I could not check was the head gasket and exhaust water jacket gaskets.
I must mention that I got some great advice on here.(KIM Maple valley)
 
Finally got around to checking out some of the suggestions here. I now have water flowing through the exhaust water jacket. The pick up tube wasn"t seated properly in the rubber grommett on the water pump. Will try it in the lake tommorow. With my laser thermometer I'm getting about 135 degrees F on the exhaust cover. About 165 on the head in a barrell. Will check in after the lake try.
 
Sounds like there is some restriction get a jug of saltaway and run it in a barrel for half an hour or while monitoring the temps the exhaust should just get warm and you should be able to hold your hand on the head for a slowcount to six.
 
Hi, so I had water around the cover but no flow to the head. I ran it without the thermostat and had water flowing to the head. Put the old thermostat back in and everything seems to be normal. Temp dropped about 60 degrees on the cover and the head. The cover is warm not hot and I can hold my hand on the head for a slowcount to six. I also have twice the amount of water coming out the exhaust hole. Thanks for all of the replies. This forum is great.
 
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