I have I believe a 1986 115hp mariner. I replaced the spark plugs for the first time after buying it. The lowest plug had silicone around it so I took it off and put all new plugs in. Hooked it up to water and it only leaked at the very bottom spark plug. Wondering if anyone has a clue what to do? It seems to run just fine but I know this is not supposed to happen. Serial number 6478314