1970 Johnson 20 hp

[Bowfishingfool]

I have a 1970 20 hp Johnson. It ran fine last year when parked. I left the gas connected( had marine stable) mixed in with it. Got it out day to make sure running good. It started easy with new plugs but was smokeing hard so I dumped the gas, drained fuel line and fuel bowl. Got new gas and mix. It's still smokeing a lot, sputters, and I'm getting some unburnt fuel and oil in my test tub. Tried adjusting the needle valve how I read it on one of the links here. I didn't get a noticeable response while adjusting it. I ended up screwing it all the way in and it was still running. Shouldn't the needle all the way in stop the gas flow?? Think I need to rebuild the carb

 

[kodibass]

Re: 1970 Johnson 20 hp

Have you checked your spark? New plugs are great but there might be other ignition issues not letting one of them fire in the cylinder, It sounds like you may be firing on only one cylinder. pull the cap off of one at a time and see if it kills the motor.

 

[Bowfishingfool]

Re: 1970 Johnson 20 hp

Have to give that a try tonight. Thanks

 

[steelespike]

Re: 1970 Johnson 20 hp

Even a perfectly running motor will foul up a tub pretty quickly.
If the coils haven't been changed they are very likely beginning to fail.
pull one plug wire at at time see if it still runs.

 

[Bowfishingfool]

Re: 1970 Johnson 20 hp

Even a perfectly running motor will foul up a tub pretty quickly.
If the coils haven't been changed they are very likely beginning to fail.
pull one plug wire at at time see if it still runs.

If coil is going bad. Is it better to change one or both? Also just trying to get it running better to sale

 

[kfa4303]

Re: 1970 Johnson 20 hp

Hi Bowfishing. Here's a handy link that can help you give your motor a tune up from top to bottom. Assuming the spark is ok on both cylinders (i.e. can jump a 1/4" gap with a bright, blue, snapping spark), I would next focus on the carb. They can/do get clogged over time, especially when using ethanol fuel. The fact that there was no effect when you adjusted the idle needle means the carb is probably dirty too. Thankfully, a carb rebuild is a quick easy job you can do yourself. You can get a carb kit right here at iboats for about $20.

Maintaining Johnson E & FD Serie

1970 Johnson 20R70E 20 hp Outboard Motor Parts

 

[Bowfishingfool]

Re: 1970 Johnson 20 hp

Pulled each of the plug wires off today. Neither one killed the engine. Also held plugs next to block and had good spark on each. Ordered a carb rebuild kit. On outboard carbs, should they be chem dipped? I have heard it both ways

 

[kfa4303]

Re: 1970 Johnson 20 hp

You can chem dip the carb if you like, but I usually just use a can of aerosol carb cleaner and a few soft brushes as needed. A thin wire is handy for clearing out the very tiny passages too. If you have an old cork float, you'll probably want to order a new, plastic one. They don't come in the standard kits, but you can buy them separately for about $10-$15.