85hp johnson misfiring

[boating2fish]

I have a '75 johnson 85hp on a 15' aries boat. The problem is in the water running down the lake I can get up to around 3000 rpms without any complications, but anything higher it begins to lung forward sometimes it will stablize and I can get up to around 4000 rpms. Anything more with the throttle it only boggs. I get back to the trailer and still in the water I check firing with a timing light all looks good and acceleration I can not get it to do anything that it does going down the lake.

 

[Walker]

Re: 85hp johnson misfiring

May have an ignition leak under load. Check for cracks and clean all coils especially the ground wires or straps. Check all sparkplug wires and check all ignition wiring for bad insulation. With engine running pull each plug wire one at a time and watch that corresponding coil for sparking to the block.

 

[bubbakat]

Re: 85hp johnson misfiring

Do a compression check and then rebuild the carbs or-check all hoses to pump and then check pump for air sucking in when running. With it running on up sometimes it seems to me like fuel problem.<br />My 85 was doing the same thing and I rebuilt the carbs and replaced the fuel lines and pump.<br />May have been a little bit of an overkill but better to do it now then be towed on lake.

 

[boating2fish]

Re: 85hp johnson misfiring

i did a compression test 120 psi on two and 115 psi on the other two. Sounds good to me. Going to check the coils and plug wires sometime this weekend. I would like to rule out the ignition before I go to the fuel side of it. thanks for any input that everyone might have.

 

[boating2fish]

Re: 85hp johnson misfiring

I have not heard from anyone else. Here is some more info for all of the johnson guyru's out there. Carb's rebuilt, syncranized by the manual,replaced one coil that had bare spot on wire, good spark on all coil wires. After all this just got back from lake and the results are first take off very sluggish up to about 3200 rpms then anything after that nothing but to me a bogg, running quite rough I might add. Stopped took off again alot better up to the 3200 rpm mark. Nothing any higher than 3200-3400 rpms without it bogging. Tried the choke and there was not any change in the way it was running. I just ran a can of engine tuner through it. Any comments or suggestion that I should go to next.