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Thread: 1972 Johnson 50
02-24-2012, 09:37 PM #1
1972 Johnson 50
Alright I have a problem with this motor. Last week it left me a drift for half a day. The lower cylinder was not firing. I thought the carb was stopped up so I pulled it off and cleaned it out real good. It looked good as new and both carbs were rebuilt last summer. It still wouldnt light that tube. I finally figured it out and it was a fouled plug. Tonight I went back to the lake and it cranked and ran fine for about 5 minutes then she died and I checked it out. Once again that cylinder was not burning. I changed the plugs right there at the ramp. Still it wouldnt run on both. I left it running on one and looked in the carbs and both were dumping fuel. I shut it off and pulled the plugs and the one thats not lighting was dry. Theres was thick black liquid running out of my prop that smelled like fuel. Any ideas??
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02-25-2012, 11:22 AM #2
That thick black liquid is unburned fuel. it should go away when the cylinder gets to fireing. You need to take a compression test to see if its holding compression. another thing to do is take the coils and swap them around and if it follows that coil to the other cylinder then it should be the coil. What type of plug are you useing? Those older fifties dined well on champion plugs QL77JC4 or JC6 gapped at 35. if you troll a lot then gap them at 40. when you get that tube light back up then do a good decarb about once a year to keep them in good shape
02-26-2012, 07:46 PM #3
I'll give it all a shot this weekend. I picked up 8 foot of fuel line, a new bulb, and an inline fuel filter to try and keep the carbs clean. I was a little dissapointed because when I pump up the bulb the fuel filter fills up then when I quit pumping the filter empties back down the fuel line. Dont have a leak anywhere. Even while the motors running the filter ends up empty. I'm stumped.
02-26-2012, 08:39 PM #4
what happened to the other posts you and i had on here as for the fuel running back into the tank the diaphram in the pump may have a pin hole in it.
02-26-2012, 08:41 PM #5
02-26-2012, 09:04 PM #6
I was wondering. I swore I had posted about the filter before. Thought I was losing my mind.
02-26-2012, 11:38 PM #7
yep. I notised that also, I even was working up a fishing trip tommorrow with a member and its all wiped away from history too
02-27-2012, 09:07 AM #8
hmm Paul the cyber dog ate our knowledge' alright paul get back in the dog house
02-27-2012, 08:31 PM #9
Do you know where to get a fuel pump or fuel pump kit for my motor? I've looked everywhere and it seems all thats out there is one for a 1978 model. I pumped the bulb up and fuel came out on the vacuum side of the pump so I guess its getting around the diaphragm. I'm wondering if this was my problem from the beginning. The pump may have been pumping enough to supply the top carb, but was starving the bottom carb.
02-28-2012, 10:30 PM #10
Sierra Marine Engine Parts Catalog
This is who I mdeal with they have always treated me good and about as reasonable as any one They have a place on their site where you can contact them and they will help in any way they can that fuel pump is most likely you problem with it loosing fuel.