johnson 48 problem

[Jbridered]

I have a 1993 johnson 48 compression is 125 on both cylinders carbs are spotless just soaked them. Engine starts fine but wont take throttle. Pulled bottom plug wire and no difference in sound but has spark on both cylinders. I put top spark plug in bottom cylinder and still no difference. Any advice? Thanks

 

[oldcatamount]

Re: johnson 48 problem

Double check the linkage placement. It's very important that both throttle plates begin to move at the same time.

 

[Jbridered]

Re: johnson 48 problem

Thanks im gonna check that. Also there is two holes to mount the cable for the throttle and i put the cable in the bottom hole.

 

[Jbridered]

Re: johnson 48 problem

I checked and both plates move at the same time. Put in new spark plugs. Old plugs looked good and clean but were wet. Cranks right up but starts acting eratic when i pull up throttle lever or put in forward. Priming bulb makes no difference.

 

[oldcatamount]

Re: johnson 48 problem

("Pulled bottom plug wire and no difference in sound but has spark on both cylinders.") How are you checking for spark? Are you using an "air gap" tester set to 7/16th inch? There should be a very visible, bright blue, snap of electricity showing when you crank the motor. Testing a plug by grounding it to the motor is deceiving sometimes. Sounds like your motor is dropping a cylinder. A motor (of that size) will start and idle very nicely on one cylinder but will not respond to the throttle.

 

[Jbridered]

Re: johnson 48 problem

Engine runs on just top or bottom cylinder. New spark plugs are wet when i pull them. Top carb spits a little out of top little jet with air breather removed. Water comes good from t-tale and near prop but not on lower unit exhaust. Could it be reeds or exhaust blocked?

 

[Jbridered]

Re: johnson 48 problem

Could the powerpack be working but just not good enough?

 

[Jbridered]

Re: johnson 48 problem

Could the reeds be stuck open causing wet plugs and not able to take throttle?

 

[oldcatamount]

Re: johnson 48 problem

I seriously doubt the reeds are the issue here. When you say the plugs are wet, do they smell like gasoline? Look really close at the plugs when you take them out. If you are getting water in one of the cylinders, there will be tiny droplets of water showing around the plugs base. Also, the plugs will look like they have been steam cleaned. We know the head isn't warped because of the compression numbers. How are you checking the spark?

 

[Jbridered]

Re: johnson 48 problem

The plugs are just wet with oily gas. I didnt use a spark gap testor but guess i will try and find one tomorrow. So if spark doesnt jump 7/16 then powerpack is the issue? Thank u for helping me.

 

[oldcatamount]

Re: johnson 48 problem

You can get an air gap spark tester from any auto parts store ($10 or so). It could be the pack, but, I would guess it's an ignition coil or a bad plug wire. The tester will show you the strength of the spark at both cylinders. If one of them is weaker than the other, look at the plug wires closely (if you could run the motor at night, it might show you a shorting wire or connection).

 

[Jbridered]

Re: johnson 48 problem

It would be nice if it were the coil. I tryed some other plug wires i had from another motor and there wasnt a difference. I also found that the red wire from the rectifier was melted so i changed it. Thank you very much for the help. I am gonna get a spark gap testor tomorrow and check the coils. I have an 1983 evinrude 50 so i wonder if i could use the coils off of it to see if they are bad.

 

[oldcatamount]

Re: johnson 48 problem

Go ahead and try the old coils. I'm not sure if the "bolt on" pattern will be the same but, I'm sure you can rig it up to test them. Just be sure to ground them well.

 

[Jbridered]

Re: johnson 48 problem

Did a test using spark gap tester set at 7/16 and it showed good on both cylinders. I gave up and brought it to the shop.

 

[nascar fan]

Re: johnson 48 problem

Keep us informed what they find wrong for the help of us that have common issues.

 

[Jbridered]

Re: johnson 48 problem

Mechanic told me the powerpack was bad and is charging me $320 and said the stator could aslo be bad but he wanted to try the pack first. He said it was hitting the rev limiter. I wish i would have changed the pack myself but being that it had very good spark i didnt. I also wish i would have checked the spark with and inline spark tester while the motor was running to see how the spark changed when given throttle. I will give an update when its done to help others.

 

[Sixmark]

Re: johnson 48 problem

Take it somewhere else, if he cannot test the stator without puting another powerpack in then he is just throwing parts at the potential problem instead of doing an actual diagnosis.

They have test procedures for stators and powerpacks for a reason.

 

[Jbridered]

Re: johnson 48 problem

He ordered a powerpack without even pulling the flywheel. Its a little late now. Lesson learned.

 

[Jbridered]

Re: johnson 48 problem

Just to update it was the powerpack. Since it had good spark i had my doubts but it fixed the problem.