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1971 40hp 2 stroke evinrude, NEED ADVICE.

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Daven030

New member
Hello, i have a 1971 40 hp evinrude 2 stroke that i am having problems with. The motor is on a 1988 alumacraft 14' deep v lunker DLX and the bottom plug fouls out very rapidly after putting a new one in and along with that the motor has very low power it moves the boat at little more than walking speed. Both cylinders have been compression checked and check out at 115 for both. The engine starts up and idles fine but like i said just has no power and the bottom plug fouls. Has anyone ever had a problem like this and if so what do you think the issue is? Thanks in advance i appreciate any help.



Anyone think running a hotter plug maybe the j6c in place of the j4c would cure the bottom plug fouling issue?
 
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Do a spark check.----A proper spark check !---------Force the ignition system to try and jump a gap of 1/4" or more.-----First step to take !
 
racerone said:
Do a spark check.----A proper spark check !---------Force the ignition system to try and jump a gap of 1/4" or more.-----First step to take !
Click to expand...



I just realized that the low speed and high speed fuel adjustment could be off that's why the bottom plug fouls out. Also, if that was way out of whack would that cause the engine to have low power at wide open throttle?
 
Answer the question !------Does spark jump a gap of 1/4" or more ????------The low speed mixture affects both cylinders the same.------The high speed mixture affects both cylinders the same !!!!!!
 
If we are to help you we need specific answers to our questions. Saying it has spark is not the same as saying it has 1/4" spark. So thank you for the answer now.

My question for you is which cylinder is the fuel pump on, on that model? If it is on the bottom cylinder, that could be the culprit. A leaking diaphragm will dump too much fuel into the cylinder. Another thought is the vacuum cut-out switch affects the bottom cylinder.

In any case, your fouled plug is a symptom, not the root cause, so a different heat range plug is not the cure. Also, your lack of speed is because it is running on one cylinder, as the plug shows. There are several possible causes, not the least of which is water intrusion into the cylinder. Or a hole in the crankcase. But much more likely is an ignition problem (the reason for demanding an answer about the spark) If you cannot find anything else wrong, it is time to pull the flywheel and check the ignition system, spark or no spark.
 
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