" Mike,
I'm no e
" Mike,
I'm no expert, but an over-rich mixture could cause that.
First thing I'd do is check to be sure the choke isn't sticking - the butterfly's should open evenly on your carb's as you push the throttle. With the throttle wide open (while the engine is not running) take a look at where the butterfly's are positioned; then push the key in for choke (don't start it or turn it over, just activate the electric choke), check to be sure the butterfly's re-open. Try that a couple times to be sure it is not an inconsistent problem.
Also make sure that the carbs are in sync with eachother - the butterfly's should open and close all at the same time as they are throttled.
You probably want to be sure you are running the correct mix - 50:1 (allways use oil designed for outboards) , with a tank of good gas - I like 89 octane. Bad gas or a bad mix probably wouldn't ignite very well.
If that's not it, your low speed jets, I believe, are adjustable; turn them in a little and the mixture gets leaner, turn them out a little and it gets richer. On my 1986 115, it's a flat head screw on the right side of each carb.. If your plugs are all getting fouled, the problem is across the board, try turning each adjusting screw in (clockwise) just a notch - mabye 1/8 of a turn. If you do this while it's running, it will be minute or two before the change is noticeable.
If the adjustment seems to help, keep adjusting until things seem right, else just keep track as you adjust and put them back just where they were. In the manual I have, it says you want to make the mixture as rich as possible, provided the engine will run evenly and not "load up" (foul plugs etc). An over lean mix means poor lubrication.
Hope that helps; You may want to give it a day or two before you try anything, there's a couple mercury experts around here that may have a better idea for you.
Jon "
