1990 Mercury 115 4cy Only Running on 2 Cylinders

rustykey

Recruit
Joined
Jul 5, 2013
Messages
2
I have a 1990 Mercury 115. I believe it is what most call the "2+2" 115. Serial number is OC235298. I have owned it for slightly over one year and had zero problems with it. I run it on my 17' Astro Bass Boat. The prior owner had it rebuilt and I have all documentation from the rebuild. I know it was bored all new cylinders installed. I don't have the rest of the paperwork with me to see all that was done. The last couple of months it has been a little difficult to start but fired off every time after choking it a bit. I took the kids out tubing the other day and it started running poorly while on the lake with them. It struggled to start and would die but I could start it right back up run the rpms up a bit and run it down to idle and put in gear and off we went. We were out for a few hours and it did this sporadically. We finished up and loaded all the goodies up and headed back to the dock. It was about a 10min ride. I was running at about 5000rpm and it sounded great. I was watching the temp and water pressure and all was good. I got 200yards from my boat launch and it just died. I was able to start it back up but would quickly die. I started it again and was able to run the rpms up to around 3k but it sounded pour. I could tell it wasn't running on all 4 cylinders. I shut her down and used the trolling motor back in. The next day I took it down to the launch and got it started again...barely. I was able to run it up to 3k and hold it there. I pulled the top two plugs (what I am going to refer to as #1 and #2) and no change in it. I pulled the bottom two (#3 and #4) and they were both firing. I was hoping that it was just bad coil packs. I checked the coil packs and all are good. The wires going to #1 coil pack have power but it will not send power to the plug. I wired the same #1 pack to the #2 wires and it sparks fine. Does that have something to do with the 2+2? So essentially, I have spark to 2, 3, and 4 plugs (from the top down) and when it gets running up to 3k rpm I only have 3 and 4 sparking. Does this have to do with the 2+2 stuff? I am at a loss and cant figure it out. I have read on the forum and cant find another thread with my symptoms. Hope it is something simple. Sorry if my post is confusing, I don't know much about outboards. Thanks ahead of time.

Rusty
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,590
Re: 1990 Mercury 115 4cy Only Running on 2 Cylinders

Has nothing to due with 2+2 as that done thru carburetion, sound like you have a switchbox problem. Go to CDI website and download troubleshooting manual and test you electrical.
 

rustykey

Recruit
Joined
Jul 5, 2013
Messages
2
Re: 1990 Mercury 115 4cy Only Running on 2 Cylinders

Ok, will do. I will come back with my findings.
 
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