60 hp Merc. #2 cylinder problem

OK, I'm at a loss now. 60hp 3 cyl. Merc 1984 model. Just rebuilt. Runs fine until under a load, then #2 cylinder quits firing or fires intermittently when rpm's reach about 2500. I have now replaced the stator, the trigger, the switch box and the coil. I have adjusted and readjusted the carbs a dozen times and checked the fuel pump twice over. It still falls off between 2500 & 3000 rpms. All three cylinders are showing 120 psi compression with no other noises or issues, so my rebuild is holding together. What the heck am I missing?!! I've never had this happen before and now I am at total loss.
HELP!!

Re: 60 hp Merc. #2 cylinder problem

then #2 cylinder quits firing or fires intermittently

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Your description does not make it clear if you clearly determined that the spark is quiting/firing intermittantly and if so, how you determined this. Determining if the problem is ignition related is a good first step in troubleshooting. You can use a DVA meter to perform some tests and/or move a few ignition parts around to see if the problem moves to a different cylinder. If you eliminate ignition failure as the problem, you can then move on to troubleshooting for fuel/mechanical related causes and ask for more advice on just this. Just my thoughts...


The shop manual for your motor will have a pretty good guide on how to test the ignition system. If you do not have one, the below linked guide will help too.

http://dolphinmarineservice.homestead.com/Ign5.html

http://dolphinmarineservice.homestead.com/Ign4.html

http://dolphinmarineservice.homestead.com/tech.html