Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !!

I have a 1995 Johnson 48hp. 2-stroke. Ran great till short time ago. While at dock in neutral motor will rev up and down with little loping at high speed. But once i engage motor into forward and give it full throttle she only goes maybe half way. Any help would be great. Fuel problem? or Something in Ignition (coil pack)?

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

Howdy.

Welcome to iboats.

You probably have a dead cylinder. Outboards lie when not under load. Could be ignition or carb. Need to troubleshoot her.

Good luck.

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

JB said:

Howdy.

Welcome to iboats.

You probably have a dead cylinder. Outboards lie when not under load. Could be ignition or carb. Need to troubleshoot her.

Good luck.

Click to expand...

Thanks
Gonna try checking plugs, and then compression.

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

When it's acting up, pull one plug wire at a time and see which cyl isn't firing. That will also tell you if you have spark or not.

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

Thanks guys for all the help. I pulled 1 wire at a time with the motor running. Top plug changed nothing. Pulled the bottom wire and motor stalls out. Hopefully bad plug, but if not? Bad cylinder? Should i do a compression check next?, or get new plugs and retry first?

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

Oh and yes by the way both have spark!

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

I would shoot a litttle premix fuel in the top carb and see if the engine surges some. If it does then it is a fuel issue.

Pull the fuel pump line from the pump to the carb off and with the lanyard/kill switch in the off position crank the motor with the hose in an old pop bottle. You should get strong steady surges of fuel from that line. If you don't suspect the fuel pump. BE CAREFUL you can get splashed pretty badly if you don't keep the line way down in the bottle. Stop cranking the instant you see good stong surges.

Another way to test the fuel pump, if the boat is in the water, is to take it out and try to run up to speed, when it falls off pump the ball and if it surges back suspect the fuel pump. If the fuel pump tests show the pump is OK, I think pulling the carbs for a cleaning or rebuild is a good next step.

Also check the fuel filter it could be clogged and not letting sufficient fuel flow.

You could also have an issue with the tank or hose, try a portable tank and different hose before you pull anything off the motor.

Re: Johnson 1995 48hp revs fine when not in gear, but in gear wont go full throttle !

Do a compression test first to make sure you have something to work with.