Wierd Problem

[woodnknots]

Okay, I posted on this before, but now I've got more info. I posted it as motor surging before.

After running my 1978 55hp Johnson for awhile, the rpms will suddenly back way off to mid range or so, then intermittently go back to wot for a few seconds and back to mid range. It's hard to tell exactly if I'm losing a cylinder or if it's just the rpms because I don't have a tach.
Anyway, if I shut the motor down for a few seconds, then start it back up, it's fine for a little while (maybe 2-3 minutes) then it starts again. So I shut it down and try again. So far, every time I've had to shut it down twice only, and then the problem is gone all the way to the dock.

I've replaced the wiring harness (had a problem getting the starter to work, thought it might have been connected), the CD unit, and the fuel pump. I'm thinking it's probably carbs, but if it's really just dropping RPM and not one cylinder, then what would cause both carbs to have a problem at the same time?
The guy I bought it from thought that the reed valves might be bad (don't know why, he's never taken anything apart).
I'm not doing anything with it right now, as I'm deploying in 3 weeks for 7 months and with 2 motors on it, it works well enough to get me to my fishing spot and back. I'll dive into it when I get back, but I'm looking for ideas, hopefully one I can try without pulling the carbs apart!

 

[1730V]

Re: Wierd Problem

A shorted ignition coil will create the symptoms you describe. You are probably losing a cylinders full output.

 

[woodnknots]

Re: Wierd Problem

I considered an ignition coil, but it's my understanding that coils are usually either good or bad? What could cause a coil to work and then intermittently not work?

 

[Solittle]

Re: Wierd Problem

Coils are easy to check by swapping them & following the problem.

 

[1730V]

Re: Wierd Problem

Heat causes coils to act up. They can be intermittant or not provide enough juice to jump a gap, at speed.

 

[woodnknots]

Re: Wierd Problem

I was going to do that today before I took the boat out, but I need to pull pins from plugs to swap them. Where can I get the pin removal and insertion tools?

 

[Evinrookie]

Re: Wierd Problem

Sounds similar to the problem I'm currently having. When I try to get up to mid or high throttle I'll lose power and then kind of start surging (stalled once). If I back it down it runs fine. If I putt-putt around a little while and then give her gas it has enough to get up on plane for a few seconds then starts losing power again. It's almost as if the low throttle cruising allows enough gas to build up for a short burst but that's all.

The previous owner installed an electric fuel pump in lieu of a primer squeeze ball. My thought is that the electric pump can't keep up with what the engine needs at higher throttle.

I'm going to replace the fuel line and put a primer ball back in. Hopefully it's that simple.

Your problem may also be fuel delivery. I'm a real rookie at outboards and your issue may be different. Good luck. Keep us posted when you find out the problem.

 

[Evinrookie]

Re: Wierd Problem

Oh and I love the quote. One of my favorite movies ever!

 

[woodnknots]

Re: Wierd Problem

any chance this could be a problem with the reed valves? A buddy of mine suggested that. At this point I'm open to anything that doesn't involve me tearing down the carbs. I want to take the boat out this weekend, and I am working 12-16 hour days in prep for deployment. I took the boat out this past Saturday for a short trip, and it didn't like it one bit.

 

[clemsonfor]

Re: Wierd Problem

it can definityly be carbs and can definitly be a coil tearin up, if they get hot they may not work right and cause a mis of a string of missed, the coil can be arcing to ground. If you have a carb problem running it without getting gas flow to a cyl means not oil is getting there either if its a 2 stroke careful running a fuel restricted engine!

To E boater, take the electric pump off it will pump enough but is not neccisary the suction pulls gas there is no pump needed the ball only primes before starting to ease cranking, cranking will also fill the carb bowls without pumping the ball itll just take longer to start. If the original fuel pump is not working you wont go wide open itll be bogging at full throttle!

 

[w2much]

Re: Wierd Problem

I had the exact problem . Irked me all summer. Thought it was the fuel pump, replaced it, thought it was the carbs , I rebuilt them. No luck, so I started thinking coils, CDI, stator. Tested them all and they were OK. I found a hairline crack in my fuel connecter. Try a new fuel line its cheep. I spent about $200.00 I did not need to.Sounds like a fuel problem to me. Good Luck.

 

[woodnknots]

Re: Wierd Problem

I had the exact problem . Irked me all summer. Thought it was the fuel pump, replaced it, thought it was the carbs , I rebuilt them. No luck, so I started thinking coils, CDI, stator. Tested them all and they were OK. I found a hairline crack in my fuel connecter. Try a new fuel line its cheep. I spent about $200.00 I did not need to.Sounds like a fuel problem to me. Good Luck.

When you say fuel connector, are you referring to the connector to the outside of the motor or the connection between the pump and the carbs?

 

[kjdunne]

Re: Wierd Problem

All fuel connections and hoses. Start at the tank and inspect every connection and every inch of hose to the carbs. A little air leaking into the system at any point will cause problems.

 

[F_R]

Re: Wierd Problem

Woodnknots, it is dropping a cylinder. What I can't tell you is why. Could be ignition, such as a coil, or could be carburetion or fuel delivery. Since you have a separate carb for each cylinder, only one dirty carb is needed to make that associated cylinder cut out. But I really would rather think it's an igniton problem. You have tried a new set of spark plugs haven't you?

Prepare that thing for storage before you leave. At the very least, put some fuel stabilizer in the gas. I'd rather you drain it out though. 7 months is pushing it for the stabilizer. And fog the powerhead. And report back in when you get home. Prayin' for ya!