Replacing spark plug wire

[wallihunter]

I recently purchased a used boat with a 1992 75hp Mariner 3 cyl. The motor idles rough at times and seems to load up with fuel at low rpm's and when the throttle is opened up it coughs a little then runs great at WOT. Today I was replacing the spark plugs and noticed the top spark plug wire didn't fit like the bottom two. In looking inside the boot I could see the clip inside was bent over so there was not good contact when the plug wire was attached to the spark plug. I am guessing this may be the problem for the above issues...any thoughts? I looked at where the spark plug wire connects to the black box and couldn't tell if this pulls out or not. What is the best way to replace this wire and is it something I could tackle myself? Thanks in advance.