1997 Merc 115 ELPTO 2-stroke 4-cyl. cuts in and out at cruising speeds

Gfisher1

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Apr 30, 2017
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just cruising on flat water, one cylinder is cutting in and out. This has been happening for the last couple of years. Fuel is good, starts good, idles good, etc. Reviewing the generic manual, looks like it could be the CDI, an injector, or the RPM limit module faulty. I never run it at WOT (5200), but at 3400-4200. Problem is, if I take it to a fix-it shop, it has to sit for 3 weeks in a field before they get to it. Not acceptable. Any help would be great.
 

Texasmark

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Dec 20, 2005
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Manual for that engine says that the cross over where you go from 2 to 4 cylinders is 2500 rpms. If yours isn't setup properly, for whatever reason....something is wearing or getting carboned up, or corroding, then it may keep 2 cylinders off line up at your cruising speed. If crappy fuel it could be the carbs getting flakes of crap which come and go for an example.
 

racerone

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Dec 28, 2013
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Put a timing light on # 1 cylinder.-----Run till motor misbehaves and observe the light.----Repeat the test with 2 / 3 / 4 cylinders .-----Post what you find.
 

Gfisher1

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Apr 30, 2017
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Thanks for the reply's. I think I'd have a hard time with a timing light skipping across the water at cruising speeds. Wish I could. This problem is not a periodic interruption, it is a sustained event that occurs for 10 to 30 seconds at a time. Perhaps the 2 to 4 cylinder switch could be at fault, but that has always operated correctly (as far as I can tell). That's why I initially am leaning towards the CDI. Could I be correct?
 

racerone

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Dec 28, 2013
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???----Perhaps you misunderstand.-----The timing light would be laying on a seat and you observe the behaviour of the light to look for ignition issues !!!----No there is no electrical switch that changes it from 2 to 4 cylinders.------The bottom 2 carburetors do not feed the proper amount of fuel to fire at low speeds.
 
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