I have a 1991 mercury 90 HP 3 cylinder.I have the in dash 6 wire switch.motor starts great But when I try to turn the key switch off it some time won't shut off and sometimes it take a little time in the off position then it shuts off.I figured it was the switch,so I ordered a new 6 wire switch and installed it.But Its still doing the same thing.I took off all the ground wires and cleaned them, thinking maybe it was corrosion but still no help.I looked in my Selco Manual but I can't find any information on it.I'm thinking maybe a kill switch or something in that area ,but thats just a guess.Any information or steps I should take,or switch tests any thing would be helpful at this time.Thanks in advance for any info.