Surging Johnson 6 hp.

[jitterbug127]

I have a 1976 Johnson 6 hp motor. I am having trouble with intermittent surfing at wide open throttle. It will run strong wide open then get weak. I’ll throttle down and I can throttle back up to wide open throttle strong only for it to surge again. This happens under load and running in a barrel. I rebuilt the entire magneto including all new points, coils, condensers, plugs and wires. It had a rebuilt carburetor and new fuel pump. I took the fuel pump off and put it on my 4 hp to make sure it was working and it has good performance in my 4 hp, so I don’t suspect the fuel pump is the issue. Would it make sense for the float or needle to not be seating correctly with this? I’ve taken carb apart twice, cleaned twice blown air through every orifice and even removed the Welch plug. I think the carb is completely clean. I’m open to suggestions. Thanks! Rob

 

[Crosbyman]

have you tried hand pumping fuel when it does start to falter ?
Tank vent open ? and working ? hose is good ?
needle clip on the float is installed ?
cooling OK ???

 

[jitterbug127]

I tried hand pumping and bulb remained firm whole time.
Tank and vent are open and working good hose
Needle clip installed
Cools just fine. She pumps great

 

[Crosbyman]

did you wire clean HS jet and main HS tube

 

[saltchuckmatt]

did you wire clean HS jet and main HS tube
View attachment 394101

Agreed, sounds like a fuel issue.

 

[jitterbug127]

did you wire clean HS jet and main HS tube
View attachment 394101

Top one yes, bottom one I didn’t know existed! Thanks. I’ll try it and repost back

 

[Crosbyman]

make certain the bottom fat donut #21 is installed to !!

do not use a big wire ... use carb cleaning tools or small mono line in jet orifices. make certain float is not upside down ... it should drop level with the carb bowl.

 

[airshot]

You mentioned rebuilt carb....did you rebuild or bought it rebuilt ?? Has this rebuilt carb been setup to factory specs ?? Do you have a factory service manual to get the right adjustments/ settings ?

 

[jitterbug127]

You mentioned rebuilt carb....did you rebuild or bought it rebuilt ?? Has this rebuilt carb been setup to factory specs ?? Do you have a factory service manual to get the right adjustments/ settings ?

I rebuilt the carb. I don’t have a book: just replace all the parts in the Crowley marine kit and turn the low speed know out 1 and 1/2 turns and fine tune from there. If there is more I’m missing that’s news to me. I probably need to download the red book from the aomci sites I’ve got a service book for a 1980 15. I’m sure it’s not really helpful

 

[oldboat1]

When it acts up, touch the top of the head to see if it's overheating. If you can't hold your fingers there for a few seconds, it' too hot. You may need to change out the impeller.

 

[jitterbug127]

When it acts up, touch the top of the head to see if it's overheating. If you can't hold your fingers there for a few seconds, it' too hot. You may need to change out the impeller.

It has a brand new water pump that pumps incredibly well. It had a clog in it that I had to resolve last fall, but that’s working great. I’ve also replaced the thermostat.

 

[Crosbyman]

I probably need to download the red book from the aomci sites...

Garry Spencer's site and downloadable RED BOOK is no more ... this site has it for $20

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

there are plenty of utubes on the subject anyway.

 

[Crosbyman]

pumping lots of water is fine but.... lack of cyl. jacket cooling water could still be a problem causing overheating. the only way to find out is touch it has suggested or scan it an infrared thermometer .

btw lots of diffdrent opinions on this but Seafoam could be tried. It certainly cleared up my snowblower surging problem two years ago and it never came back. just dump a can in your tank.

 

[jitterbug127]

I probably need to download the red book from the aomci sites...

Garry Spencer's site and downloadable RED BOOK is no more ... this site has it for $20

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

there are plenty of utubes on the subject anyway.

I guess I missed the mark on that book. Ill get it ad download bought. Thanks for the heads up.

 

[jitterbug127]

pumping lots of water is fine but.... lack of cyl. jacket cooling water could still be a problem causing overheating. the only way to find out is touch it has suggested or scan it an infrared thermometer .

btw lots of diffdrent opinions on this but Seafoam could be tried. It certainly cleared up my snowblower surging problem two years ago and it never came back. just dump a can in your tank.

Crosby as always I appreciate your help. I've had the motor on the water and its never got hot. I can touch it and its fine.

 

[Crosbyman]

glad to help ..sometimes I eat crow .
you do not suspect fuel but bad fuel is a known cause of surging. is your's fresh ?? did you check the bottom HS orifice jet ?.

 

[jitterbug127]

glad to help ..sometimes I eat crow .
you do not suspect fuel but bad fuel is a known cause of surging. is your's fresh ?? did you check the bottom HS orifice jet ?.

I checked the bottom jet and it looked pretty good. I soaked the while carb in Berryman for a couple hours last night and just to be sure. My fuel is probably 2 or 3 months old. I have a 4 HP motor that I am working on now at the same time that has no surging, so I think the fuel is ok. This 6 hp was doing this exact same thing in the fall when it was pushing my boat as well and that was brand new fuel from the station that day.

 

[Crosbyman]

well if not fuel quality, not a plugged up carb, good hose good filters , good fuel pump etc....ignition could be a cause. condensers even new ones can be bad or react to heat build-up. VOM testing of condensers is not conclusive unless truly bad.

points being mecanical less suspicious. flaky coil maybe ?

but bactrack a bit... what was the initial problem that got you replacing all these parts to begin with. Not clear if surging was the reason or the outcome of all these parts being replaced.

 

[jitterbug127]

well if not fuel quality, not a plugged up carb, good hose good filters , good fuel pump etc....ignition could be a cause. condensers even new ones can be bad or react to heat build-up. VOM testing of condensers is not conclusive unless truly bad.

points being mecanical less suspicious. flaky coil maybe ?

I put in all new Sierra points, coils and condensers, a few months ago suspecting the same thing. I still have the same symptoms even after rebuilding the entire magneto. I also put new coil wires and spark plugs.

 

[jitterbug127]

well if not fuel quality, not a plugged up carb, good hose good filters , good fuel pump etc....ignition could be a cause. condensers even new ones can be bad or react to heat build-up. VOM testing of condensers is not conclusive unless truly bad.

points being mecanical less suspicious. flaky coil maybe ?

but bactrack a bit... what was the initial problem that got you replacing all these parts to begin with. Not clear if surging was the reason or the outcome of all these parts being replaced.

I rebuilt magneto for 2 reasons.
1. Id never rebuilt a complete magneto and this motor is in really great shape so I wanted to try it.
2. It was surging and it thought it the surging might be motor running on one cylinder when it would just get intermittently weak.