75hp Mariner 4cyd 2 storke 1986, Misfire but has Spark

Hi
I have a 75 mariner 4 cylinder 2 storke.
I have from 125psi to 130psi on all 4 Cylinders. My number 2 cylinder has spark but its not firing the cylinder. It Idles rought. I had to turn up the Idle to 1300 rpm just for it to run.
I pull the number 2 sprak plug wire off when its running There is Spark and is no change in the motor rpm,s or running. When I pull 1, 3 , or 4. the motor almost stalls. I put in a new Coil on #2 cylinder. and no change,
I bought a new Switch box and replaced it. No change it still does the same thing.
The motor run rought at Idle. but seems to screem real nice out on the lake running wide open. Its on a 16'7" alum Sea Nymph. So maybe 3 cylinders pushes it good. Not sure there. its a new boat to me.
I also went thru the Carbs. Replaced the floats and needles, and cleaned the cars out real good.
Any IDEA's Not sure what to do at this point.

Dan~ from Michigan

Re: 75hp Mariner 4cyd 2 storke 1986, Misfire but has Spark

I suspect that an idle passage in #2 carb still has a clog in it that will not allow enough fuel or air to pass through. You are going to have to go through that carb agaiin very carefully using a quality spray carb cleaner followed by an air hose to ensure that every passage is clear.

Re: 75hp Mariner 4cyd 2 storke 1986, Misfire but has Spark

Hello
Thanks for the Responce. That Carb is like Brand new. I suspect my Reed Valve. Reason Why? when the Motor runs it kind of Spays a fine mist of Gas out of the Top Carburator. Cylinder 1 & 2 run off the top carb. 2&3 Run off the bottom Carb. I swap out Carbs and it did the exact same thing. Cylinder 2 not firing, and mist of gas comming from Top Carb.
I was just looking into Changing the Reeds Valves. Its a huge job. Looking for a way to test them before I Split the Block.
Thanks for the INFO
Dan~ Lake St Clair MIchigan.

Re: 75hp Mariner 4cyd 2 storke 1986, Misfire but has Spark

Do you know were I can buy Reeds for this 75hp motor.
there is no Info for parts on this Website. I just ran the motor again. NO Fuel going to Cylinder 2. When I hit the Carb with Spry it stalls. The carb is almost puking gas out of the Intake. its a fine mist.
Dan~ the Great Lakes MIchigan

Re: 75hp Mariner 4cyd 2 storke 1986, Misfire but has Spark

Dan if you are losiing the cyl. only at idle and everything else is OK it's probably a reed. If you get to 2000 and the fuel plume goes away thats also a good sign it's a reed.

Re: 75hp Mariner 4cyd 2 storke 1986, Misfire but has Spark

Just to let everone know. I fixed the motor . It lost 1 reed pedal. I had to Split the block to fix it. found the broken Read in the block with a Magnet. Got luck it did not get sucked thru.
Its running great now. Thanks for all your help.
Great Lakes Dan Michigan.