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1985 115 hp mariner

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Brian O

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Hello, I have just bought a 115hp mariner 1985 model. It starts and runs OK at idle but when you take off it cuts in and out. I put new plugs in it and replaced three pump ball. It sounds. Electrical to me.check e'er check screens in fuel system to. I am a mechanic but not on the outboards, does anyone have any ideas on How and what to perform some checks ? Thanks
 
First off thanks for the response, it isn't like shutting the key off or bogging, it sounds like not all the cylinders are firing, it like cuts in and out. Stumbling. It goes and gets on plane but during take off miss's bad then seems to smooth out some once it gets planed out.
 
it sounds like not all the cylinders are firing,
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The spark plugs can give you a wealth of cylinder operation. Check compression first, spark next then fuel from the carbs. If compression is even (all cylinders w/in 10%) and spark is good(jumps 7/16" gap on a test board) then rebuild all of the carbs.
 
i am experiencing the exact same thing. can you keep me in the loop ? we got our motor used from a shop, and it has a warranty on it....i will send the results on what we find.
 
Guy, was Merc using the 2+2 ignition on these back in 75?

Could be a combination of 1) needs a tune up 2) stator or switchbox getting tired OR 3) owner not used to that "crossover from 2 to 4 cylinder mode".
 
On a 2+2 the 4 plugs always fire and the bottom 2 only get a wee bit of fuel at idle.----------I think 1985 would be an inline 6-------But posters can help themselves with more information and serial # to get the good answers.
 
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I think it's an I-6 TOP engine per racerone. I have a 2002 115 HP 2+2. It behaved similarly w/a drop in RPM last summer so did all 4 carbs in Dec. and found a chunk of plastic holding open a reed in #4. All the carbs had sludge in the bowl. Runs much better now.

Brian: you need to clean and sync. each carb to ensure each cylinder is getting fuel w/oil...very important to get the fuel/oil mix even if it isn't firing right. You don't want a dry cylinder running at 5,000 RPM. Check YOUTUBE and see how simple it is to rebuild the carbs. Buy or make a spark test board in order to compare all of the spark wire outputs side-by-side. You'll see if there is a weak spark right away.
 
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