79 Johnson 85hp losing power under load

[Mud Fish]

1979 85hp Johnson V4 Seahorse<br /><br />Recent Repairs:<br />Replaced starter and solenoid<br />Replaced spark plugs/cleaned carb<br /><br /><br />Current Problem:<br />Engine starts fine, idles fine, and will run like a scalded dog for miles ... then goes to what seems like half power. Will max out rpm (9) using throttle lever only, however, when put in gear and under load, only gets around half as much power(4). Will spit and sputter sometimes, then resume normal running, until it happens again. Have tried with two different fuel sources to rule out bad fuel. Fuel supply from tanks through filter is ok. Just cleaned the carb, replaced spark plugs and wires. Possible power pack? coil? or am I missing something? Any help would be greatly appreciated.

 

[Rudy Brown]

Re: 79 Johnson 85hp losing power under load

When it starts losing power, will choking it improve it? Just tryin to isolate the problem, fuel or spark. I had a problem like yours once. It turned out to be a piece of clear plastic that would suck up to the pick up tube in the tank and starve the motor for fuel.

 

[Walker]

Re: 79 Johnson 85hp losing power under load

Clean all the coil ground straps and the block where they bolt on. Check coils for cracks.

 

[emdsapmgr]

Re: 79 Johnson 85hp losing power under load

When it starts to act up, a couple of simple tests: 1. try squeezing the primer bulb. If it picks up and runs well, could be the fuel pump. 2. put a timing light on each plug wire. all four should have a strong, constant flash.

 

[Mud Fish]

Re: 79 Johnson 85hp losing power under load

Thanks for all the suggestions. I'll grab my tools, a couple of adult beverages, and see what I can figure out. I will post results from various tests/attempts. Thanks again folks!

 

[Walker]

Re: 79 Johnson 85hp losing power under load

Also try running it without the hood on. Those older V4's didn't have much clearance between the hood latches and the lower sparkplug wires and sometimes a damaged sparkplug wire would short to the hood latch while under load.