I have a 90hp 1978 merc. I installed the gaskets at water jacket cover and rebuilt carbs the engine doesnt leak any more and starts easy but seems to have an intermitant miss on two plugs. I used a spark tester and #4 and#6 sometimes miss a spark all the others seem to be firing fine. The seloc manual isnt much help here as far as trouble shooting. I took the cap and wires off a 115 merc and still have the same thing. What to look for now? The 115 is the same ignition system no points and one coil.