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83 60hp johnson bottom cylinder dead.

H

Hainesbri

New member
I'm scratching my head with this. I have a 83 johnson 60 up. Ran fine a year ago. Winterized it, went to get it ready in spring and noticed the fuel pump was leaking. I replaced the fuel pump and brought it to the lake only to find it idled great and ran fine at slow speed, but would not power up and plane out. I started with new gas, but that didn't help. Next I looked at plugs, which were good. Eventually found that if I pull upper plug wire while running, engine dies. I changed plug, wire, coil, and even tried a new power pack, but still have a dead lower cylinder. I haven't put a compression tester on it, but did pull the plug and run it and I couldn't hold a thumb over the hole, so I have (some) compression. I did notice that bottom carb is leaking, not sure if it's related to the problem or not. All I can figure is that I'm not getting strong spark at bottom cylinder, or its getting starved for fuel. Clearly I'm not an outboard mechanic, but would like to fix the issue myself. Any help would be much appreciated.
 
Pulling the plug wire off the top cylinder causing the engine to die indicates the "bottom" cylinder isn't firing.

Compression is always taken with a compression gauge with "all" of the spark plugs removed at cranking speed.... not with your thumb while the engine's running. The slightest scratch on your thumb would have air pressure going into it that would blow your hand (and arm) up to the size of a football... think about it! We need to know the psi readings of the individual cylinders... saying it's good or great, whatever, doesn't really tell us anything.

Assuming you have compression and spark that will jump a 7/16" gap on both cylinders, what remains is carburetion and I would suspect that the bottom carburetor has fouled while sitting due perhaps to not being winterized properly in that area.

Pay particular attention to the high speed jet, located horizontally in the bottom center portion of the float chamber. Carefully clean it with a piece of single strand steel wire. Fuel must flow thru that jet freely before it can flow to any other fuel passageway.
 
joereeves said:
Pulling the plug wire off the top cylinder causing the engine to die indicates the "bottom" cylinder isn't firing.

Compression is always taken with a compression gauge with "all" of the spark plugs removed at cranking speed.... not with your thumb while the engine's running. The slightest scratch on your thumb would have air pressure going into it that would blow your hand (and arm) up to the size of a football... think about it! We need to know the psi readings of the individual cylinders... saying it's good or great, whatever, doesn't really tell us anything.

Assuming you have compression and spark that will jump a 7/16" gap on both cylinders, what remains is carburetion and I would suspect that the bottom carburetor has fouled while sitting due perhaps to not being winterized properly in that area.

Thanks for the reply. I appreciate any help I can get. I'm mechanically inclined enough to turn a wrench, just not enough of a mechanic to always know where to put the wrench, so like I said, thanks much. At any rate, I don't have a comp tester, so I'll have to see if I can hunt one up. Your diagnosis of the carb sure seems right however, as it seems like it would make sense then that the fuel is flooding the bowl and not making it into the cylinder. All I can do is try and see what happens.
Click to expand...
 
Suspecting that fuel is not flowing thru the bottom carburetor.... to test.....................

With the engine running and the bottom cylinder NOT firing, simply insert two fingers into the bottom carburetor throat, acting as a manual choke. If the rpms pick up, that proves the point.

If, on the other hand, with the carburetor face plate off and the engine running, air is being forced out the carburetor throat with each downward thrust of the bottom piston... then obviously a reed plate (leaf valve) is damaged, in which case, remove the intake manifold to repair that item.
 
joereeves said:
Suspecting that fuel is not flowing thru the bottom carburetor.... to test.....................

With the engine running and the bottom cylinder NOT firing, simply insert two fingers into the bottom carburetor throat, acting as a manual choke. If the rpms pick up, that proves the point.

If, on the other hand, with the carburetor face plate off and the engine running, air is being forced out the carburetor throat with each downward thrust of the bottom piston... then obviously a reed plate (leaf valve) is damaged, in which case, remove the intake manifold to repair that item.[/QUO

Took the face plate off and placed two fingers in carb throat as suggested with no change in performance. Shot a short mist of carb cleaner in the throat and the rpms picked up long enough to burn the mist.
Click to expand...
 
Hainesbri said:
Took the face plate off and placed two fingers in carb throat as suggested with no change in performance. Shot a short mist of carb cleaner in the throat and the rpms picked up long enough to burn the mist.
Click to expand...

Okay... your reply statement above indicates that either fuel is not gaining access to the carburetor... OR... (and most likely), the carburetor needs cleaning and rebuilding as needed.

Be sure to manually clean the high speed jet that is located horizontally in the bottom center portion of the float chamber as fuel must flow thru that jet freely before it has access to any other fuel passageway.
 
joereeves said:
Okay... your reply statement above indicates that either fuel is not gaining access to the carburetor... OR... (and most likely), the carburetor needs cleaning and rebuilding as needed.

Be sure to manually clean the high speed jet that is located horizontally in the bottom center portion of the float chamber as fuel must flow thru that jet freely before it has access to any other fuel passageway.
Click to expand...

Thanks for the advice. I'm planning to take the carbs off this weekend and clean them, new gaskets, etc.
Also planning to take a look at the reed valves as well. I noticed some fuel sitting in the throat. I'm a novice, but if the reed valves are bad, would that mean they are allowing fuel and air back out the throat rather than keeping them in the cylinder?
 
Hainesbri said:
Thanks for the advice. I'm planning to take the carbs off this weekend and clean them, new gaskets, etc. Also planning to take a look at the reed valves as well. I noticed some fuel sitting in the throat. I'm a novice, but if the reed valves are bad, would that mean they are allowing fuel and air back out the throat rather than keeping them in the cylinder?
Click to expand...

Yep, you betcha! Sometimes a leaf valve here & there might be just a few thousands or so off from sealing to the plate, but normally crankcase pressure will slam that shut... BUT... if a leaf valve has a piece of it missing or broken off altogether... yeah, with every downward stroke of the related piston, air will come rushing out the carburetor throat like it was blown out of a shotgun.
 
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