04 40hp electrical problem... I think...

Merc40fisher

Cadet
Joined
Jul 2, 2013
Messages
14
Hey guys, ok here we go. I have an 04 mercury 40Hp 2stroke 3cyl that I believe loses a cylinder in rough water. Iv changed all fuel lines, rebuilt carbs and pump, even ran different fuel tank and fuel primer bulb to make sure it was not a fuel system problem. But when getting into a light chop it acts as if it looses a cylinder. Suddenly changes pitch and slows down, then suddenly returns back to normal. It continues this untill you get to calmer water. It also does this while crossing another boats wake. It's any time the motor starts to shake it'll cut a cylinder out. My question is how do I test all the electrical stuff on here to see what's the problem. Iv checked all connections and grounds and changed spark plugs. My tach would not read right a while back and someone told me to check the 2 yellow wires coming from the stator under the fly wheel and sure enough the connections were almost completely melted in half. So I changed then but does the same thing still. How can I check coil packs, or stator or anything on here. I'm getting tired of it now. And being its such a sudden loss and pick back up, iv ruled out fuel problems. It has to be an electrical connection or something failing somewhere. Anyone ever seen this or fixed anything like this before??? Thanks guys
 

carholme

Rear Admiral
Joined
Sep 4, 2010
Messages
4,845
Re: 04 40hp electrical problem... I think...

What is your engine s/n and do you have the service manual? If not, send me a PM with an email address and I can send you a copy.

Have you ruled out the possibility of a sticking carb float/needle valve when the water is rough?

Gerry
 

Merc40fisher

Cadet
Joined
Jul 2, 2013
Messages
14
Re: 04 40hp electrical problem... I think...

PM sent. I don't really know if iv ruled out the float or not. Iv tore the carbs down and checked everything 3-4 times. It all looks brand new, nothing sticks or look abnormal.
 
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