1999 Mercury 115 2+2 running issues

[bwguardian]

The engine has just been broken in running double oil and now filled tank with nothing but fresh gasoline...oil injection still hooked up. The carburetors have been gone through twice due to this issue as of now. The engine starts right up and idles good, especially after the link and sink. You can hit the throttle and feel the 2nd set of carburetors start flowing. It started having hesitation in the 3,000 rpm up, but if I hit the throttle a little it goes away for a bit...probably the throttle enrichment. It will also stop if I pull the throttle back to below 3,000 rpm. I did rebuild the fuel pump a couple days ago and thought that may solve my issue but no go. I have changed the fuel water separator several times thinking that might be an issue. I pulled the plugs today and installed a new set. I noticed the top three were dark and a little wet while the bottom had alot of black carbon powder on it...remember this is a 2+2 engine. I have also replaced the primer bulb and installed all new fuel line from the tank to the engine. The primer bulb stays solid before starting and while running.

I will be taking it out later today or tomorrow and see if the new plugs made a difference and try and get some video. It does sound like ignition to me with the stutter noise and occasional missing and/or jerking while on plane. I haven't found any videos showing how to test the cdm units and/or plug wires, but do have a 7 function multimeter for such.

 

[racerone]

Run with a timing light one cylinder at a time.------Observe the flashing as you speed up.------Make sure you installed the correct parts in the fuel pump.

 

[bwguardian]

Wind has been blowing here so finally got a chance late this afternoon to put the boat in the water and run for 20 minutes. It ran better than it has ever ran...no rattling and/or chattering at mid range...so the plug change may have fixed it. Planning on fishing tomorrow afternoon after the rain passes and see how it does on the long run. I will pull the new plugs tomorrow and check them prior...the old plugs didn't look good, especially #4 which was dry carbon deposits. I suspected a bad coil and hopefully the new plugs aren't a patch...