99 merc 115 intermittent miss

scott2712

Recruit
Joined
Sep 4, 2007
Messages
1
hello to all. I read this forum all the time but this is my first question. I have a 1999 Mercury 115. It seems to have a miss. But only sometimes.when you first get on it you can hear and feel it miss and then it will kick in and go. I can get the rpm's up to 4450 (need to change the prop) and get her to cruising speed but you can feel and hear the miss. It fluctuates back and fourth. At first, I was possibly thinking a chunk of something in one of the carbs but it also idles rough and misses at idle. Some kind of ignition problem? Any ideas would be greately appreciated:)
 

renny1

Petty Officer 1st Class
Joined
Jul 10, 2007
Messages
219
Re: 99 merc 115 intermittent miss

sounds like a plug not doing its job or crud in the carbs
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 99 merc 115 intermittent miss

I adjusted the idle mixture a touch fat on the top two carbs and make sure that the accelerator pump is adjusted by the book

Curious what prop you're running, my 13 1/2 X 22 Lazer II seems a bit too small, GREAT holeshot but overall top speed is down and RPM too high

135 compression on all
NGK BPR7HS @ .035 almost too hot, will go back to BPR8HS @ .035
WOT 5900
 
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