Phree Refill
Cadet
- Joined
- Apr 24, 2009
- Messages
- 12
Re: 1976 Johnson 6 Horse Cooling System Conundrum
Well I finally got back to work on the beast last night. And great news. It is now cooling itself. What was wrong with it? Your guess is as good as mine. Although I do have a theory. I believe it was right on par with what Jay mentioned earlier. I took off the housing plate that lets you see into the exhaust chamber of the power head. This housing plate has grooves cut in it that direct the water flow around the side of the powerhead and up to passage that goes into the thermostat housing. These grooves are not very deep. I looked down where the water enters this housing plate from the powerhead; there were a lot of scales and what appeared to be small paint chips. The paint chips were presumably what flaked off the engine when it was getting really hot. I cleaned out all of the scales and paint chips and scratched off any additional build-up that I could from the inside of that passage.
When I turned the housing plate over so I could look at the grooves in it, I noticed that the groove cut in it that allows water from the powerhead to flow up to the thermostat housing was very small. It was no deeper than the thickness of one of the gaskets. I scrubbed the inside of this housing plate out real good so that there was no debris left in any of the grooves anywhere. With both the cylinder head off and this housing plate off, I hooked my drill up to the motor and spun it in my trash can of water. I didn't even have to spin it fast or very long and water started coming out of the passage in the powerhead. When I saw this I knew that the problem definitely was not in the lower unit anywhere for the water flow and pump were just fine. I ran it like that for a few seconds just to flush out any other small debris that I might have loosened up.
Next I put the housing plate back on again and but left the cylinder head off. I spun the engine again with the drill. Again, it pumped just fine and it didn't take much time or effort to do it. Plenty of water was coming out of the passage that goes to the thermostat housing in the cylinder head. So next I put the cylinder head back on and spun it again. Water flowed just fine into the thermostat housing and would continue to do so for as long as I ran the drill. Seeing no blockages with everything basically put back together, I decided to go ahead and put the thermostat back in and fire it up. I got it started and ran it for prolly 30 seconds before I killed the engine and it pumped a fair amount of water out the blow hole the entire time. It wasn't a ton of water but it certainly was more than just the droplets and steam like what I was getting before. So I decided to fire it up and run it for longer. I ran it for prolly 3 minutes straight and it pumped water out the blow hole the whole time. I would compare the water flow to about the same as what you would get when you fill a cup up with water from the water dispenser on your refrigerator. It was a fair amount. More importantly, I could actually hold my hand on several parts on the engine and exhaust shaft while it was running and not burn my hand. Before, the entire engine would get super hot. Now the only thing that gets to hot to hold your hand on is the cylinder head right by the spark plugs but any engine gets that hot. I would estimate that the hottest part of the engine is nowhere near 200 degrees. Maybe 140~160 range.
I believe the reason it would stop pumping water is exactly like what Jay said in an earlier post; one of the scales or paint chips was laying in the water passage of the housing plate. Initially, the water pressure wasn't enough to move it but after a few seconds the water pressure would pick up and that chip/scale would get lodged in small passage that allows water from the powerhead head to get to the thermostat. When it would lodge, it would block all the water flow. Then when the engine was shut off, the chip would fall back and the passage would be reopened again. At least that is what I assume the problem was. In any case, the engine is pumping water just fine now! I think it was a steal for 125 bucks! Its in superb condition and runs great.
Thank you Jay, whaler, crxess, and tashasdaddy for all your help. Especially Jay and whaler. I wouldn't have even thought to do half of the stuff I did had it not been for your suggestions. Each one was very helpful. Now my boat will be complete! Thanks again!
Well I finally got back to work on the beast last night. And great news. It is now cooling itself. What was wrong with it? Your guess is as good as mine. Although I do have a theory. I believe it was right on par with what Jay mentioned earlier. I took off the housing plate that lets you see into the exhaust chamber of the power head. This housing plate has grooves cut in it that direct the water flow around the side of the powerhead and up to passage that goes into the thermostat housing. These grooves are not very deep. I looked down where the water enters this housing plate from the powerhead; there were a lot of scales and what appeared to be small paint chips. The paint chips were presumably what flaked off the engine when it was getting really hot. I cleaned out all of the scales and paint chips and scratched off any additional build-up that I could from the inside of that passage.
When I turned the housing plate over so I could look at the grooves in it, I noticed that the groove cut in it that allows water from the powerhead to flow up to the thermostat housing was very small. It was no deeper than the thickness of one of the gaskets. I scrubbed the inside of this housing plate out real good so that there was no debris left in any of the grooves anywhere. With both the cylinder head off and this housing plate off, I hooked my drill up to the motor and spun it in my trash can of water. I didn't even have to spin it fast or very long and water started coming out of the passage in the powerhead. When I saw this I knew that the problem definitely was not in the lower unit anywhere for the water flow and pump were just fine. I ran it like that for a few seconds just to flush out any other small debris that I might have loosened up.
Next I put the housing plate back on again and but left the cylinder head off. I spun the engine again with the drill. Again, it pumped just fine and it didn't take much time or effort to do it. Plenty of water was coming out of the passage that goes to the thermostat housing in the cylinder head. So next I put the cylinder head back on and spun it again. Water flowed just fine into the thermostat housing and would continue to do so for as long as I ran the drill. Seeing no blockages with everything basically put back together, I decided to go ahead and put the thermostat back in and fire it up. I got it started and ran it for prolly 30 seconds before I killed the engine and it pumped a fair amount of water out the blow hole the entire time. It wasn't a ton of water but it certainly was more than just the droplets and steam like what I was getting before. So I decided to fire it up and run it for longer. I ran it for prolly 3 minutes straight and it pumped water out the blow hole the whole time. I would compare the water flow to about the same as what you would get when you fill a cup up with water from the water dispenser on your refrigerator. It was a fair amount. More importantly, I could actually hold my hand on several parts on the engine and exhaust shaft while it was running and not burn my hand. Before, the entire engine would get super hot. Now the only thing that gets to hot to hold your hand on is the cylinder head right by the spark plugs but any engine gets that hot. I would estimate that the hottest part of the engine is nowhere near 200 degrees. Maybe 140~160 range.
I believe the reason it would stop pumping water is exactly like what Jay said in an earlier post; one of the scales or paint chips was laying in the water passage of the housing plate. Initially, the water pressure wasn't enough to move it but after a few seconds the water pressure would pick up and that chip/scale would get lodged in small passage that allows water from the powerhead head to get to the thermostat. When it would lodge, it would block all the water flow. Then when the engine was shut off, the chip would fall back and the passage would be reopened again. At least that is what I assume the problem was. In any case, the engine is pumping water just fine now! I think it was a steal for 125 bucks! Its in superb condition and runs great.
Thank you Jay, whaler, crxess, and tashasdaddy for all your help. Especially Jay and whaler. I wouldn't have even thought to do half of the stuff I did had it not been for your suggestions. Each one was very helpful. Now my boat will be complete! Thanks again!