1987 Johnson 48hp doesn't run well with Cowel on.

[Benjamin12]

Hello everyone. I have a 1987 Fishn Ski Barge with a 1987 Johnson 48hp. I bought it non running. Cleaned out the carbs and new fuel system. When I ran the boat, it would not plane and sounded like the engine was running rich. I took the cowel off, cleaned the spark plugs and ran it. The engine ran well with no issues. The moment I reinstalled the engine cowel, it had the same problem. I took off the cowel and it run great. The cowel is not obstructed. The carbs do have the silencer installed. Has anyone had this issue before? If so how was it remedied? Thanks.

 

[juno pierrat]

could be a bad gasket between engine block and mid section, pulling in exhaust gasses

 

[racerone]

Could be sparkplug lead shorting to the cowling latch..---Yes I know cowling is plastic.----And it is a good idea to install a new impeller on a new to you motor.-----Change gear oil too as gearcase is not known to be robust.

 

[Benjamin12]

Could be sparkplug lead shorting to the cowling latch..---Yes I know cowling is plastic.----And it is a good idea to install a new impeller on a new to you motor.-----Change gear oil too as gearcase is not known to be robust.

Impeller and gear oil are new.

 

[Benjamin12]

could be a bad gasket between engine block and mid section, pulling in exhaust gasses

I've never heard of that but makes sense. I'll look into it. Is it too much to change it out?

 

[Benjamin12]

Impeller and gear oil are new.

I'll look into that. Perhaps removing the latch and securing it with a strap

 

[tphoyt]

Check all the wiring to be sure nothing is lose and able to short when the cover is on.
check for lose Insluation in the cover that could get sucked into the intake on the silencer.
Run it at night in the dark and look for anything arcing move the wiring around with stick if need be. Video of the motor running would be helpful. Both with the cover on and off.

 

[racerone]

Replace the plug wire.----I don't think removing the latch is a good idea !!!