Outboard problems on a 40HP 2 stroke merc

[dada2727]

I have a 40HP 2 stroke oil injected Merc, it's either a 2004 or 2005 and am having some problems. The problem only occurs at a higher RPM, most noticably at full throttle. When I have it wide open, it seems like it's missing or not firing on all cyclinders (its a 3 cylinder) but I just had it tuned up and the carbs cleaned. It will run fine if I continuously adjust the trim up, down, up, down...and so on, but as soon as I stop adjusting the trim it starts doing it again. I'm thinking it might be electrical because I just spent $350 getting water removed from the carbs apparently.

 

I had this problem a couple years ago and I had it fixed and they told me it was something like a "starter coil" but I'm not completely sure. I just remember they showed me some wires that were melted together.

 

Any thoughts?

[solopaddler]

Although you said the carb's been cleaned it sure sounds like a gummed up carb to me.

I'd try one those carb cleaners that you mix with the gas. That's worked for me in the past...

[ohhenrygsr]

so with the miss firing does it still run or just die out?

[dada2727]

still runs, never stalls or anything...just sounds like its missing. Any recommendations on carb cleaner additives?

[Fisherman]

Seafoam! Should be able to get it at Carquest or NAPA. Sounds like a Stator coil, makes power..

[Sinker]

Its funny you post this, because my 2 stroke 40 mariner started doing the same thing. Only at WOT. I can run 3/4 throttle no problem, but as soon as I crack on it, she misses.

 

I have no idea what it is. I was going to post the same question.......it will idle, troll, run at any speed but wide open no problem. As soon as I crank it open it misses, so I back off.

 

I don't think running seafoam is going to help, I run it in every tank of gas, and I decarb it a few times a year too. She's as clean as a whistle, and the carbs are mint.

 

I almost thought it was starving for fuel at full throttle?

 

 

S.

[Garnet]

Try pumping the fuel bulb when wide open might be just losing pressure.

 

Garnet

[fisher]

Are you using fuel without ethanol...?

 

I swear the issues I had with my 2 stroke 40 HP Merc all started when ethanol was introduced to gas. Since I had it rebuilt, I have switched to the highest octane gas from Esso, Petro Canada or Shell who do not put ethanol in them (they only put it in their lower grade fuels).

[ohhenrygsr]

Are you using fuel without ethanol...?

 

I swear the issues I had with my 2 stroke 40 HP Merc all started when ethanol was introduced to gas. Since I had it rebuilt, I have switched to the highest octane gas from Esso, Petro Canada or Shell who do not put ethanol in them (they only put it in their lower grade fuels).

 

 

I have only found that Shell and Ultramar High test have no ethanol never heard that Esso or Petro didn't have it either

[fishermccann]

I agree put in super gas , no more problem.

[dada2727]

Well apparently it was just a spark plug, but we'll see. If it is, I feel kinda stupid but before for some reason I don't think it will be the end of it. Thanks fisherman, the Stator coil was the part I was thinking about that I replaced last year, some wires were melted together. To be continued........

[Fish4Eyes]

Doesn't high octane gas make your engine run hotter? Is this recommended by marine mechanics?

[fishermccann]

it has no alcohol to attract the water.

[dada2727]

How many people just run regular fuel?

[Fisherman]

Me, in everything unless the mfgr specifically indicates a higher octane requirement. Google what octane actually does in the combustion cycle of an engine and what kind of motors it is intended for.

[danbouck]

I use regular and add stabil ethanol treatment

[Sinker]

I use regular and add stabil ethanol treatment

 

Ditto!

 

My problem was a bad o ring on the fuel filter cansiter. So far so good. If I pumped the ball while going WOT she ran fine, so I started at the tank, and worked my way back to the carbs and found the split O-ring.

 

S.