I have a 1994 Mercury 40HP outboard that just won't start easily when it's cold. Once I get it started it's fine until it cools down again. Then I have to reprime and rechoke and then it finally starts. I put new plugs in and they don't help. I just winterized the engine and when I pulled the plugs, 3 out of 4 were dirty. The forth plug looked brand new. The plugs have only been in since late June. Any suggestions?

The clean sparkplug isn't firing. 3 possibilities. Bad coil, bad sparkplug, bad switchbox. Unfortunately the bad switchbox is the most likely. It might be worth having a dealer check it out. You probably don't have the meter to test the switchbox. Diagnostic time and repair time should total around an hour of labor. The switchbox is rather expensive. That's why you want it checked before you just up and replace it. Being an electronic component, it isn't returnable if your old one is good afterall.