Have a Johnson 9.9,4 stroke outboard that after running for 15 min.Starts missfiring,then stalls.Will start after cooling off.Ihave replaced coil,fuel pump, primer bulb,spark plugs,and spark module .
Couple of possible problems. I would tend to lean to wards carbon build up on the piston . What happens is over time you will gain carbon , as the engine runs it super heats and when its hot enough it will cause the gas to ignite at the wrong time and actually stall the engine. Imagine you are pushing a rotary door in the mall and every time you pass the enterence to the mall another person jumps in and helps push ... everything spins easily . . Then some clown jumps in and gets caught in the frame ... everything stalls. To fix this you will need to take the head off and clean out the carbon. Might take a bit but it can be done . Had this happen to a mechanic friend of mine... he repaired a 9.9 got paid for the job and the motor would run for 20 min and quit couldn't figure it out to save his soul. Until we put our heads together. Checked every possible thing only to figure out it was a carbon problem.
How do you fix rewind on Johnson seahorse 4hp
Usually, replace the recoil spring.
You also, may be able to increase the wrap tension by:
1) pull spark plug (easier to manipulate spinning the motor)
2) wrap the extra loop of rope around the start pulley gear.
sometimes there is a bracket, etc. to work around
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