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I have a 2000 40hp 4 stroke Yamaha. I was not getting fire on the #2 cyl. I just replaced the ECM unit last Fri. and took it out to run. It ran rough at first then after about 10 min. of running it felt like you hit a NOS button and took off better than it ever run. I'm guessing it was some bad fuel in the line that cleared it's self out. Well Sunday morning I head out to fish at daylight and it starts and runs like a champ. On up in the day the wind got up and made the water rough. As I head out of a cove and get in the rough water the motor starts to act like it did before I replaced the ECM. Loses some power and runs rough. I took it to about 1/4 throttle and rode the waves out to some calm water. When it got calm I opened it up all the way and it ran good, but about half way across the calm water it started getting rough again. I get home and pull the plugs and #2 is not firing again. #1 and #3 have fire. I pull the coil wire off of #3 and put it on #2 and get fire, same thing with the #1 wire on #2, so I know the coil is good. I talked to a Yamaha mech. and told him everything and he said "Yamaha electronics very rarely cause problems" that he would start with the fuel. It's hard to start on the fuel knowing the the #2 cyl. has no fire. Where do I go from here? I'm thinking it is the pulser coil or stator. Anybody ever had a problem like this?
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Hi
I had a similar problem fault finding took for ever it turned out that it was the little o ring on the fuel quick disconnect was letting in air and water into the fuel line. cost me $10 in the end, after i'd cleaned and dryed the fuel tank replaced the fuel lines, filter and water seperator.
the way i found it was to put a direct hose from the fuel bulb the the fuel bowl on the engine.
only took me a month to find it!!!
Andy -
It sounds like your problems might be twofold. try running on a portable fresh filled tank of gas, and see what happens. If that cures some of the problem, look at the stator/ and pick up- coil. I had a similar problem with a 1985 Mariner 200 hp and it turned out to be both the stator and a suspicious pick-up. Even if the pick-up looked good, I figured since I had it all apart, why take a chance, so I changed it
Don't worry, you will figure it out.
DennisComment
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Will a faulty stator or pulser coil do any damage to my ECM?Comment
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