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1966 33hp Johnson running only on one cylinder

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Albertabound

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Hello all, I took the boat out for the first time this year (model RXE-14D),I'm having issues. Once on the water I gave it full throttle; having running on one cylinder for about 30 sec. the second one kicked in and away we went. After about half an hour the second one quit for good. Thought it was bad spark but new plugs made no difference. We did figure out its not plugs, nothing was wrong with the other ones(my dad is a mechanic and helped me with most of this problem solving). Compression test showed both cylinders at 110, same as its always been. Pulled it apart because we thought fuel valves were stuck, all leaf valves are in good condition. Looked at pistons and rings to confirm compression which they did. Cranked motor without the carb on to watch the leaf valves and they all work correctly. Figure it might be the top seal on the crankshaft but that doesn't make sense with what we see. The top cylinder is the one that doesn't work. Put it back together and ran it, motor jerks several times a minutes when the second cylinder ignites for one stroke. Took the fuel pump off while running and covered the hole through the intake cover; seems to be alot of hot exhaust back pressure. Now we discovered when we squirt WD-40 direct into the carb sometimes we can get the second cylinder to run for about 20 sec. Now I took a second look at the valves and can see no issues. I know the safety switch does not work but that shouldn't effect things. Besides helping out on our problem can someone tell me what exactly the cut-out switch does? Thanks in advance, Andrew
 
It does not make no sense that the second one kicks in and out,and if you take the fuel pump off, it cant run without gas going to the engine,and thats what the fuel pump does.the top cylinder i think should be your number one cylinder.Mabe try to explain better what is going on.If it fires then dont fire on a cylinder try checking your wiring connections.
 
Time to pull the flywheel for inspection !!!--------This is so common that these motors run on one cylinder.----------There is a coil , point set and a condenser for each one ( a duel system )----------Remove coils and check for burn through to the mag plate.-----This happens all the time.
 
I realize I didn't make it clear but both pistons have spark. I cranked the motor with the plugs out but hooked up and the spark is fine. Dad has an electronic gadget that measures the spark traveling through the wires when the plugs are threaded in and the motor's running and there is no issue(spark is good). As for the fuel pump the carb holds enough fuel in a cavity to run for about half a minute. The motor worked good last year, its got to be some funny deal. It seems like that top cylinder doesn't get fuel but there's no problem with stuck valves and until the valves the fuel is one source for both pistons.
 
OK then use a timing light on it and go for a spin and see which cylinder looses spark !-----------------Not a mystery to me.
 
The "electronic gadget" I referred to was a timing light, I had totally forgotten the name until racerone mentioned it. Several times now between pulling stuff apart we run it for 15-20 minutes in a barrel of water, just the same as taking it for a spin. The top cylinder is the one that doesn't run, we know this for sure( take the wire off the top cylinder while the motors running and nothing changes. Take the bottom spark plug wire off and the motor dies.). Spark is excellent on both cylinders, fuel valves and supply seem good and there are no issues with compression .
 
OK, then check the spark with a " spark checker "----------If spark does not jump a gap of at least 1/4" with a snap you can hear ------You have " no spark "--------------The other possibility is something holding a reed valve open.-----------That would not show up on a compression test !!!!
 
Problem solved racerone! I checked the spark, Dad suggested the same thing (check spark) yesterday but I was working. Now I had time and the top cylinder spark was too weak. Pulled the top off and the coil for the top cylinder was arcing through. I will change condensers, coils, and spark plug wires. Thanks for your help, first time I've used a forum before.
 
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