Mariner Surging

[Mr. Easy]

I have a 1994-90hp. Mariner outboard that surges at 1/2 to full throttle after a 15min. warmup.
My question is does anyone think the ethanol is raising cain with the carbs-only one of three plugs seems darker at the electrode-the top on a 3 bbl. carb!
I replaced the fuel pump diaphrams with Merc parts,replaced fuel filter and primer bulb. Will this require a bench repair or can I add chemicals to the gas to clean up the carbs?Has anyone else had this problem? Oh yes the fuel pump bolts had the original paint on them so what does that tell you?
This motor is on a 24' pontoon-same year as motoer-maybe 100hrs. on both!

 

[JUSTINTIME]

Re: Mariner Surging

rebuild the carbs

 

[outhere99]

Re: Mariner Surging

I agree... but make sure you get a new set of floats and needle/seats. I had the problem with my 50hsp. Everything looked clean, but the foam floats were replaced with the plastic ones, and now it runs great! Make sure you replace the rubber tip needles too. Probably a good time to replace the fuel pump diaphram, and lines. If they're all the same age it worth the few extra dollars to avoid the wasted time (I wasted two weekends!)