Mercury 115 2 stroke won’t idle and runs rough.

[Tim from Newzealand]

Hey guys I’m new to the site but I’ve been googling my a** off trying to figure out what’s going on.

I have rebuilt the carbs, rebuilt the fuel pump and put new plugs in. Motor hasn’t run in a very long time, multiple years. Serial is 0C191163. Have managed to get it running now but it still won’t idle and it’s still running like crap. I’ve also noticed the 2nd plug from the top is clean while the other 3 have carbon on them. All I know about the motor is that it was running fine when it was parked up

Any tips or advice would be greatly appreciated. This is the first outboard I’ve pulled apart but I’m generally pretty handy with everything.

 

[racerone]

Step #1 in outboard trouble shooting is a compression test.----Post the actual values here.-----A clean sparkplug means----No fuel.---Too much fuel.----No spark.----No crankcase compression.----No cylinder compression.----Bad sparkplug.---Cylinder sleeve rotated ( rare )-----All easy to check in my opinion.

 

[Tim from Newzealand]

Step #1 in outboard trouble shooting is a compression test.----Post the actual values here.-----A clean sparkplug means----No fuel.---Too much fuel.----No spark.----No crankcase compression.----No cylinder compression.----Bad sparkplug.---Cylinder sleeve rotated ( rare )-----All easy to check in my opinion.

Sweet as, I’ll chuck a compression tester on it and get back to you.

 

[Tim from Newzealand]

Step #1 in outboard trouble shooting is a compression test.----Post the actual values here.-----A clean sparkplug means----No fuel.---Too much fuel.----No spark.----No crankcase compression.----No cylinder compression.----Bad sparkplug.---Cylinder sleeve rotated ( rare )-----All easy to check in my opinion.

I’m counting from the top which I’ll go ahead and assume is correct.
Cylinder 1: 110
Cylinder 2: 112 (This cylinder has the clean plug
Cylinder 3: 111
Cylinder 4: 110

 

[racerone]

Does spark jump a gap of 3/8" or more on each lead ?

 

[Tim from Newzealand]

Does spark jump a gap of 3/8" or more on each lead ?

I tested the spark with a spark tester and they were fine.

 

[racerone]

The question has not really been answered.-----I can not be of further assistance here.

 

[cyclops222]

Check the carburetor throats of all carbs for mice packing them with nesting material. My motor. Crammed full with white seat cushion material. Ran as quiet as a 4 stroke.

 

[Tim from Newzealand]

The question has not really been answered.-----I can not be of further assistance here.

Yes the spark jumps about 3/8s of an inch. I’m not super familiar with imperial so I’m guessing a bit there.

 

[Tim from Newzealand]

Check the carburetor throats of all carbs for mice packing them with nesting material. My motor. Crammed full with white seat cushion material. Ran as quiet as a 4 stroke.

I’ve had the carbs off and rebuilt them.

 

[Tim from Newzealand]

Hey guys I’m new to the site but I’ve been googling my a** off trying to figure out what’s going on.

I have rebuilt the carbs, rebuilt the fuel pump and put new plugs in. Motor hasn’t run in a very long time, multiple years. Serial is 0C191163. Have managed to get it running now but it still won’t idle and it’s still running like crap. I’ve also noticed the 2nd plug from the top is clean while the other 3 have carbon on them. All I know about the motor is that it was running fine when it was parked up

Any tips or advice would be greatly appreciated. This is the first outboard I’ve pulled apart but I’m generally pretty handy with everythi

I reset the idle screws on the top 2 carbs and I’ve managed to get it running now but she’s pretty hard starting.

 

[racerone]

Outline in detail your cold starting procedure.----On more than one occasion have I met folks who did not read an owner's manual, to learn how to start these motors.

 

[jimmbo]

Yes the spark jumps about 3/8s of an inch. I’m not super familiar with imperial so I’m guessing a bit there.

about 9 1/2mm, just under 1 centimeter

 

[Chris1956]

A real clean spark plug can be a sign of water infiltration into the cylinder.

Did you tell us the year of this motor? Is it a 2+2 motor?

 

[cyclops222]

Did you RUN COMPLETELY dry all the carburetors of gasoline at end of last time ?
Or just stop the engine and store it ?
If you just stopped the engine ? Then a lot of dried up gasoline is in all the fuel passages.