1982 35HP Johnson overheating

[copus]

Model J35RCND. I have replaced the waterpump impeller and housing. New thermostat. When running on the muffs, the exhaust cover stays cool but the block and heads are to hot to touch. I have water coming from the telltale and both exhaust ports and the prop. I removed the thermostat and no change.Where do I start looking next?

 

[petryshyn]

Re: 1982 35HP Johnson overheating

Slip a garbage can under it and fill with water. Try running in garbage can or in the lake. Sometimes hose operation is less than adequate if you don't have enough hose volume....

 

[Piscesstar]

Re: 1982 35HP Johnson overheating

what you can try is to bypass your thermastat and see if it runs cool. If it does let it run for 5 or 10 min. and then go thru the thermostat again. You can bypass the therm. by disconnecting the 2 hose at the back rear. I just did that to my motor this morning and it worked.<br /> you may have to do this a few times for it to wouk

 

[copus]

Re: 1982 35HP Johnson overheating

I ran the motor in a barrel but cylinder head got to hot to touch. I then took a compression test . The lower cylinder was 120 and the top was 70, so Ipulled the head and found oil in the water passages.This head gasket I've used <br />twice so I<br />guess it didn't hold this time.The day before had it on the river and it was going great. Revved<br />to 4500 rpm with a top speed of 30 mph.Gasket must have started to leak and then it slowly heated up and died.Will try a new head gasket and see what happens. Thanks guys.

 

[copus]

Re: 1982 35HP Johnson overheating

Update..... I replaced the headgasket and removed the thermostat.Engine runs good in the barrel but cylinder head is to hot to touch. Exhaust water and telltale are cool to the touch. Water in the barrel is cool. The water jacket on the exhaust stays cool. I blew out all passages when I had the head off and ran water through them. Seems like the water is not moving through the heads.<br />Any ideas? <br />Is there a way to backflush the head if I drop the lower unit?

 

[copus]

Re: 1982 35HP Johnson overheating

bump

 

[clanton]

Re: 1982 35HP Johnson overheating

Did you check the water deflectors, when cylinder head was off.

 

[copus]

Re: 1982 35HP Johnson overheating

Clanton.... Yes, Both deflectors were in place. In fact I replaced the top one because it looked a little burned. I also dropped the lower unit and rechecked the impeller which is new and that was in good shape. I blew air and water back through the thermostat opening and it came out at the lower pipe which connects to the pump.<br />Can you tell me the exact path the water takes when it leaves the pump? Does it enter the cyl.head water jacket from the bottom or the top?<br />Thanks for any help.

 

[clanton]

Re: 1982 35HP Johnson overheating

Remove the thermostat and housing, start engine in water, fast idle, water should gush from thermostat hole, if not you have blockage in water tube.

 

[copus]

Re: 1982 35HP Johnson overheating

clanton... I removed the water jacket cover from the cylinder heads and started engine.My buddy noticed exhaust smoke coming out of the thermostat opening. Could this be a bad power head to lower unit gasket where exhaust gas is getting into the cooling system ? I was getting water from the thermostat hole. The block runs hot and also the cylinder heads, but everything else is cool.<br />Thanks.

 

[copus]

Re: 1982 35HP Johnson overheating

^^