25 hp Johnson sneeze

[Kiscratchie]

I have a 2005 25 hp Johnson. After running the boat for 10 minutes & unable to get on plane, I realized one of the spark plug wires was disconnected & replaced it. The boat ran fine afterwards- plenty of power. The following day the engine began idling rough- sneeze & die- ran fine under throttle. Got home & pulled plugs- one wet. Not sure if the problem is due to running the motor on 1 cylinder or alot of idling? (These plugs were practically new).
Also, a buddy (mechanic at yamaha dealership) recommended swapping from Champion QL77JC4 to NGK BR9HS-10. Is it O.K. to swap from a suppressor type plug to a resistor in this type motor? Any thoughts would be greatly appreciated!

 

[freddyray21]

Re: 25 hp Johnson sneeze

may be a bad plug. a quick change is cheap and might solve the problem. If the wire was unhooked for awhile and sounds like it might have been you may have damaged a coil also.

 

[tashasdaddy]

Re: 25 hp Johnson sneeze

the motor was designed to operate with Champion plugs,

 

[crxess]

Re: 25 hp Johnson sneeze

NGK BR9HS-10 is a direct cross reference plug replacement. Motors are designed to work with specific heat range of plugs for best performance in specific applications. Manufacturer is not as important as Quality.

First change the plugs and test. Cheapest test. If the problem persist, go to the wires/coils. Running the motor in the dark with the cowl off will quickly show a shorting/arcing wire.

 

[Kiscratchie]

Re: 25 hp Johnson sneeze

Thanks for the input. I put 2 new plugs in the motor & changed the impeller this morning. Taking it out for a spin & will post back with results.

 

[tashasdaddy]

Re: 25 hp Johnson sneeze

crxess, i do not know your background, but if you are knowledgeable, on Johnson, Evinrude, Gale outboard motors, you will know that using anything other than Champion Plugs, is a known cause for misfiring problems.

NAPA auto parts even has this note on there computer system for outboard plugs. by the way NAPA has a 600 page marine catalog for parts.

 

[Kiscratchie]

Re: 25 hp Johnson sneeze

Put 2 NGK plugs in & the boat ran like a champion (no pun intended ). Idled as well as it ever has. Is it O.K. to use resistor plugs with this motor? I've heard not to use them in motors with advanced ignition/ electrical systems. I understand champion plugs are recommended, but afew people (1 a boat mechanic for 15 years) have said they foul easily in the small 2 strokes.