1972 Johnson 50

[cretus]

He folks I'm having a problem with this engine. It fouled a plug two weeks ago and I thought that was the end of it. Tonight I cranked the boat at the ramp and it ran for a while and then it stalled. I felt the head and the lower cylinder was cool to the touch so I changed the plugs at the ramp and I started it out of the water. Only one cyclinder was firing, but both carbs were jetting fuel. I pulled the lower plug out and it was dry. There was black liquid coming out of the prop and it smelled like fuel. Anyone have any input on this?

 

[jbjennings]

Re: 1972 Johnson 50

WHich plug fouled?'
Was the top cylinder cool or hot?
My suggestion would be to get a $6 spark tester and see which plug is firing and which is not, then swap coils and see if the problem follows the coil. If so, replace the offending coil. I think you probably had a weak coil which resulted in a fouled plug. IF it's not a bad coil, you'll have to troubleshoot the ignition.
Good luck,
JBJ

 

[5150abf]

Re: 1972 Johnson 50

Start at the start, do a compression check and spark check, if you have both of those it is a fuel probelm, you need compression, spark and fuel adn you are missing one of those.

If you have fuel coming out at the prop it woudl look like a spark issue but check all 3 things.

Compression on that should be over 100 and the sprark should jump a 7/16 open gap.

 

[F_R]

Re: 1972 Johnson 50

Absolutely, check the compresion before you run it any more!! It wouldn't be the first one of those that busted a piston, and won't be the last. Continuing to run it will only add to the destruction.

Hopefully, that isn't the problem and you can move on to checking the spark.

 

[cretus]

Re: 1972 Johnson 50

I have 130lbs on each cylinder. I have a bright spark also. The fuel is coming out of the jets, but not going into the cylinder. I'm now wondering if My crankshaft seals are bad and letting the fuel out in the foot.

 

[cretus]

Re: 1972 Johnson 50

Alright the boat cranked at the house. I think I'm getting trash in the lower carb. Can you put an inline fuel filter like the ones on a lawn mower right before the primary carb or will it cause to much resistance? I need to change my bulb and fuel line because its gotten stiff and may be the problem with the trash.

 

[cretus]

Re: 1972 Johnson 50

Does anyone know where to buy a fuel pump for this motor? I really want to buy a rebuild kit, but cant find one anywhere. I think I have a tore diaphragm because my fuel is leaking back down to the tank.

 

[jbjennings]

Re: 1972 Johnson 50

I got an NOS fuel pump for mine on an auction site. I would change all fuel lines on it, clean the carbs. and get a new fuel line from the tank to the motor, preferably a good quality one. You may have some ethanol problems going on. If fuel is going back to the tank, it could be because the check valves in your primer are bad, and not necessariily the fuel pump. You could put a fuel/water seperator/filter just after the primer on the main fuel line.
Lastly, how did you determine that you had good spark?

 

[5150abf]

Re: 1972 Johnson 50

Once fuel linegets so old it stars flaking off internaly and will plug your carb over and over so I would change all the ga line form the tank to the carbs putting a fuel filter just before the engine and clean th carbs one more time to be sure they are clean.

I run an inline from Autozone and haven't had a carb problem for years and the gas goig back t the tank could be the check valve like jb said or an air leak butchanging the hoseshould fix that.

Check here on iboats for a pump,the pries are usually the best you can find and the service is great.

 

[cretus]

Re: 1972 Johnson 50

I bought 8 foot of fuel line from advanced auto. Bought a new bulb also. bought an inline filter and put it right before the pump. I figured the pump was bad because I can pump the bulb and fuel comes out of the vaccuum side of the pump. As for the spark, I have no way of really knowing, but I grounded them and turned over the engine and each one lit up bright.

 

[F_R]

Re: 1972 Johnson 50

Fuel squirts out the pulse line? Bad diaphragm for certain. Repair kit 18-7820 from here at iboats SHOULD work, but is not listed as such. I'll bet it will work though.

 

[cretus]

Re: 1972 Johnson 50

Fuel squirts out the pulse line? Bad diaphragm for certain. Repair kit 18-7820 from here at iboats SHOULD work, but is not listed as such. I'll bet it will work though.

Yep thats the problem I've been running in to. Theres a replacement pump or kit for all the models all around mine but not mine specifically.