55 HP Johnson losing power

[james_shoemaker]

I have a johnson 55e76e on my pontoon boat and it works great at idle and low throttle levels, but if you open it up it runs great for 30-45 seconds then loses power dramatically. If you drop it back to idle for a minute or so you can get the 20-45 seconds again. Sounds like a fuel issue, where should I start looking?

James

 

[steelespike]

Re: 55 HP Johnson losing power

Start with the simple things first.Check all connections and connectors, check hoses, check the tank vent.
Does a little choke help.If it does then it may be a fuel supply issue.Possibly a carb rebuild may cecessary with special attention to cleaning.If squeezing the primer bulb helps you may need a fuel pump rebuild.

 

[steviecops]

Re: 55 HP Johnson losing power

Sounds like it could be a fuel pump problem. Maybe the fuel in the carb bowls can keep the engine going for 30-40 seconds at full throttle, then the pump can't supply enough fuel at those revs? When you slow down, the pump may be able to re-fill the carb bowls and you're good for another 30-40 seconds?

Like steelspike says, try squeezing the bulb next time it loses power.

 

[james_shoemaker]

Re: 55 HP Johnson losing power

I took it out again and the problem wasn't as repeatable. Neither the choke or fuel bulb helped the situation. Also now it seems to affect the idle sometimes as well. I have a bad feeling I have an intermittent ignition module problem. Will take the timing light with me tonight and see if I lose spark in either cyl when I am having the problem.
Is there a reason I would be on my second ignition module in 3 years? Is there something that kills them?

James

 

[james_shoemaker]

Re: 55 HP Johnson losing power

Found it checked and it wasn't losing spark when it lost power so I checked the carbs, there was a tiny ball of varnish in one carb bowl that was around 1/2 the size of a BB. It was plugging the main jet when the flow went up, then floating away when the flow was lower. When I got rid of it all the problems went away.

James