1987 Mercury 135 no spark cly's 1 and 4

guy858

Cadet
Joined
Aug 16, 2009
Messages
9
hi there. going on vacation this year, I got the boat out and fired it up. had problems starting it this year. fires every year.. I could get it started after a long time trying, it would to fire and kick the bendix out, but could get it started finally.. checked it out, pulled the plugs out and looked for spark, didn't have spark on 3 different cly's.. was out of time to go, called a couple of marine places, and they thought it sounded like the switch boxes went bad ? spark was out on opposing cly's, so it made sense. I got 2 new Mercury boxes, put them on and it fired up right now ! and ran fine.. went on vacation that afternoon, it ran good for 5 days, and then it was there again, last day, same thing.. my question ? can a weak stator cause the switch boxes to go bad ? I didn't have time to test the stator output, but it ran great for awhile.. I don't want to buy new boxes again ( we know how much they are $$$ ) so I'm trying to get in the right direction. I'm having trouble finding stator cranking numbers, what it should be to test it ? any help ? I'd love it !!!
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1987 Mercury 135 no spark cly's 1 and 4

Is it missing on 3 cylinders, or just on 1 & 4.

CDI has test procedures on their sight. You need a DVA meter or adapter to do it right. If it's missing on opposite cylinders, as in 1 and 4, it is typically the trigger that is bad.

If you have a trigger with a bad wire on it, just moving it around to put in new switchboxes could make it seem right, and then the trouble comes back again. It's never a good idea to spring for these expensive parts till definitive diagnostics point to the failing part.
 

guy858

Cadet
Joined
Aug 16, 2009
Messages
9
Re: 1987 Mercury 135 no spark cly's 1 and 4

it has spark on everything but 1 and 4 right now.. thank you for the help.. I do have a good meter, and will look up CDI.. at first, I had missing spark on 3 of the cyl's... now its 1 and 4 that are not firing.. thank you very much !!!
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1987 Mercury 135 no spark cly's 1 and 4

it has spark on everything but 1 and 4 right now.. thank you for the help.. I do have a good meter, and will look up CDI.. at first, I had missing spark on 3 of the cyl's... now its 1 and 4 that are not firing.. thank you very much !!!

One trigger winding is common to those two cylinders.
 
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