66 Johnson 3hp bit more advice please

R

ray 6688

Seaman
Joined
Dec 25, 2008
Messages
67
Hello all.
My 3hp Johnson seems to be running too hot when run in garbage can full of water to the correct height.
After a few minutes running the cylinder head is hot enough to burn your fingers if you hold it for a few seconds.
Have fitted new impeller,and checked pump housing for wear.
Will pump water up copper tube fine with leg removed and drive shaft turned clockwise with a socket/ratchet on splines.
Have removed cover to water entry hole in bottom of cylinder block and
water poured into hole comes out of exit hole in block.
When running water is coming out of the relief holes in the leg.
I have not removed cylinder head as bolts are very tight and seem like they will snap .
Can anyone tell me is it possible for the cooling water to run through this engine without going through cylinder cooling jackets and head?
Thank you
Ray
ps. I have made sure the copper pipe is fitted correctly at engine end and fitted a new gasket.
 
kbait

kbait

Commander
Joined
Nov 13, 2007
Messages
2,462
Re: 66 Johnson 3hp bit more advice please

Those motors don't have thermostats, just small openings in the head gasket to restrict water flow. I have found that they are hotter to the touch than larger motors at operating temp. If it doesn't boil water off the head when you splash some on it, it's probably fine.
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,224
Re: 66 Johnson 3hp bit more advice please

kbait said:
Those motors don't have thermostats, just small openings in the head gasket to restrict water flow. I have found that they are hotter to the touch than larger motors at operating temp. If it doesn't boil water off the head when you splash some on it, it's probably fine.
Click to expand...

The cylinder head on those motors is NOT water cooled, except for just around the edges. If you touch it near the spark plug you are going to get burned. Even around the edges, the water flow is not forced--it is just whatever happens to go in and out the holes in the head gasket.

Another area not yet mentioned is the flat plate on the side of the powerhead. That thing gets blazing hot and will fry a finger in a heartbeat. There is fire behind it.

I would say your motor is just fine and don't be worrying about it.
 
R

ray 6688

Seaman
Joined
Dec 25, 2008
Messages
67
Re: 66 Johnson 3hp bit more advice please

OK thank you all for your advice.
I did remove the head,not much gunge in cylinder waterways.
Having looked at water flow passages I see what you mean,the only way water can enter head is through the tiny holes in head gasket.
Will do as you advise and not bother about it,just keep fingers away.
Found the article on 3hp overhauls very interesting.
Thank you all.
Ray.
 
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