Mercury 25hp issue

[matsmad]

Hey all just picked up a 2004 Mercury 25hp short shaft. It starts easy, but runs rough. It seems to be only running on the top cylinder. If you pull the bottom lead off it still runs and doesnt change. Ive checked compression, both cylinders even 90psi, both have good spark. Could it be a fuel issue? Theres only one carby so i thought not? Any help would be appreciated! :S

[rayke1938]

Water in cylinder?What does plug look like?

Cheers

Ray

[max pwr]

Pull the bottom spark plug out, reattach the lead to the plug, start the motor and test the plug for spark with your tounge.

[rayke1938]

Wondall rd marine now based at runaway bay 33965633 or 0433422500 honest and no bull.

They will probable give opinion over phone. Mercury experts.

Cheers

Ray

[Bi_polar]

and swap the plugs around too.

[matsmad]

Haha i used my tongue and now it hurts. Swapped plugs, both good spark, sparkplug clean and wet (with fuel), just cant work it out. Will take to a machanic as a last resort already spent too much on this thing :dry:

[Uthrax]

Bad fuel??

Too much oil in mix??

Carb level too high causing bottom cylinder to flood??

[matsmad]

Good thinkin i will drain the tank and put some fresh fuel in it

[Uthrax]

Another thought could be that there is a little bit of crud or similar holding open the float valve on the carby causing it to flood

[rayke1938]

Any result yet?

Cheers

Ray

[matsmad]

Hi Ray. Sorry havent even looked at it since. We had a baby recently so my hands are full! Im gonna take it to the mechanic who services my boat i cant be bothered with it now lol

[Boatguru]

check the coil pack

[matsmad]

check the coil pack

I swapped coil packs over and still the bottom cylinder isnt firing. Im going to take it to my boat shop get him to look at it hes a guru

[dirtridder]

after every thing you have checked I would say a cracked reed or it's just stuck open.