1986 Johnson 6hp

[JPDP]

I have a '86 Johnson 6hp on a 12' jonboat. It starts on first pull and runs great up to 1/3 or higher throttle, then engine acts like it is missing. So far I have replaced the coils, power-pack, plugs, plug wires, and fuel pump. I have a carb rebuild kit but do not want to tear into that just yet unless that is most likely the problem. I have a service manual but it does not give an exploded diagram for the carb. Anyone have one that has been scanned and can send to me?

[Peter O]

and your email addres is.....?

[hondon]

Is it possible that you are simply lugging this motor?What kinda load are you puting it up against and has it always done this or did it just start?

[JPDP]

My e-mail is John.Pinkham@yuma.army.mil. And to answer the second question, the motor has done it since I bought it from a guy last year. He said it is just cavitation from the flat bottom boat, but that doesn't seem right to me, I would think that cavitation would make the engine spin up. Also the boat is not under a large load, its a narrow 12' flat bottom jon-boat.

[JPDP]

Last night I rebuilt the carburetor and took it out on the lake in hopes the rebuild would fix it. Darned if it doesn't still do the same thing. I don't have any idea what it could be now!! Any ideas out there?

[Fouled Plug]

I almost wonder if you have lower unit troubles. Does it seem to have the same symptoms throttled up in reverse? Perhaps the clutch dog or out-of-adjustment shift linkage could be the culprit. Is the prop a rubber hubbed design or shear pin on that motor?

[Chinewalker]

How's compression? Could be a blown head gasket. Is any of the wiring worn or cracked? With the motor running, make it misfire and try removing one of the plug wires (heavy gloves are a good idea!) and watch what happens. If it runs smoothly on one cylinder, then the one you pulled is the culprit. If it dies or misfires on one cylinder, then the one still attached is the culprit. What do the plug tips look like? Gunky carbon? Wet? Dry light chocolate? White? Do the test, read the plugs and get back to us...- Scott

[clanton]

Check1. Plastic roller/linkage on carbuator body.2. Small plastic hose inside carbuator.3. Link assy on timer that contacts roller on carbuator body.4. Insure throttle plate is level at WOT(wide open throttle).5. Primer system, may have bad seal.

[petryshyn]

My god man, you've spent a ton.....Try squeezing the primer ball hard when its missing. Does it get better? If she does, she's thirsty for fuel....and you might want to check:-filter-air leak in system lines-restriction in 'tank to carb' lines(install vacuum gauge in suction side of fuel pump to verify this)-debris in tankI'm getting a little worried.......just reviewed your post again.....I hope you tried a new plug. Very common to see them break down under load. also, have you checked timing synch.?good luck man......

[Peter O]

Hey there JPDP, did you get the carb diagram yet? I haven't heard if it works for you! Do you need the steps too? Let me know.

[JPDP]

Yes got the diagram, thank you, rebuilt the carb and still does the same thing. Over the weekend replaced the 6 gal tank with a 3 and replaced the fuel line/bulb. Seems like it does it when it is under a load, doesn't do it when it is not in gear. Now I'm wondering if it is slipping in/out of gear.

[Fouled Plug]

If you have eliminated the prop as a problem, take a peek at the gears and clutch dog. The teeth on the dog and/or the notches on the gear can "ramp" and make it bounce in and out of gear under load. It only take a few thousandths of wear to make life difficult. In an emergency (urgent fishing trip) I once used a cotter pin to lock the dog on an old OMC 18hp in forward and used it for a weekend until the gear and dog could be replaced. But then you have a forward only motor that is spinning the prop as soon as you fire it up, much like the old style motors. Had to watch where it was pointed when we pulled the rope!

[suzukidave]

If it's got the same carb as in the 89 6hp which I own, it can be highly finicky or at least seems so to this particular inept wrench. Problems I've experienced include the plastic bowl cracking if you overtorque the screws, and a major susceptibility to gumming up. Both resulted in a loss of top end power as well as very hard starting, although its more a lack of power than a miss. I rebuilt mine twice last year after I got old gas in it only to continue with the same symptoms. I then gave up and gave it to the dealer who ultimately couldn't explain how he fixed it. Shortly after that I left it alone for 2 months and the same problem started again. Now it's a bit of a paperweight and so I'm saving my next carb rebuild for when the salmon come back around here. if you have the same one, try rebuilding the carb a second time very very carefully, inspect the bowl closely for cracks, and make sure it's completely flushed of old gas before you reassemble.good luck