I Have A Problem

[Big Fish Hunter247]

I have 1987 40hp Johnson its overheating but the thing is I have replaced the water pump impeller, waterjacket gasket and it still overheats. This is the motor I asked about awhile back there was alot of steam comming outta the exaust port thats on the midsection. Its "peeing" just fine the water comming outta the is ice cold but when you touch the powerhead and it has been running for awhile its hot. I know there is alot of calcium deposits on the boat Im wondering if some of that is in the cooling system? if so how can I get it out?

Big Fish Hunter247

[Ufatz]

How do you KNOW it is running TOO hot? Exhaust (cooling) water is cold and engine runs fine, right. The power head will be hot because it has been running. Engines GET hot! I'm not saying you don't have a problem and I make no pretense of being an OB mechanic but sometimes we IMAGINE we have a problem. I say if exhaust cool and flowing, motor operating properly and not seizing I would go with casual but frequent monitoring.

Dat's all.

[Big Fish Hunter247]

I know its running hot because it shut down on me today and wouldnt run till after it cooled off The mist comming out of the exaust port is hot too

Big Fish Hunter247

[foulpole18]

I have a 89 25hp johnson that was doing the same thing. I had a mechanic look at it and ended up having to replace the water pump and it needed a new head gasket. Not sure if thats whats going on but it may be something to look into.

[boatfixer]

Have you replaced the thermostat? The other thing that can happen with the OMC's is if they get hot enough they can melt the deflecters away in the water jacket.

[Eric Wettschreck]

Is the thermostat good?

[Big Fish Hunter247]

where is the thermostat located?

[boatfixer]

Item #12 is the thermostat

[Big Fish Hunter247]

thanks boatfixer I didnt even know there was a thermostat

[Eric Wettschreck]

Some guys have removed their thermostats thinking, like on some cars, it will keep the engine cool. DO NOT fall into this trap. No thermostat will actually overheat the engine.

Just lettin ya know in case ya didn't know.

[Big Fish Hunter247]

Wouldnt no thermostat mean wide open flow and constant cooling?

[marine_man]

That's correct, but it doesn't allow your engine to get up to the temperature it was designed to run at, causing other issues.

marine_man