I have an 1989 three cylinder 50 h.p. merc that has weak firing on two cylinders. I have done some troubleshooting per the following.<br />1.) New plugs<br />2.) repositioned spark plug wires to try to move problem<br />3.) repositioned working coil with suspect bad coil.<br />None of these has moved the problem, problem remains on the two cylinders that originally had weak firing.<br />Tested spark firing by pulling plug wire off of spark plug, one at a time, and can see spark on all plugs. Once I get to the plug that is firing properly engine immediately cuts out. Apparently only that plug is firing, although some spark is getting to all plugs. <br />So at this point I believe it is safe to assume it is not the plugs, plug wires, or coils? Where to I go now? <br />Incidentally, 3 years ago I put a new switchbox on for coil firing?
