Mariner 115hp starting problems

[hore1984]

Hi I live in Australia and cant seem to find any help over here so thought I would try on here, I have a 115hp Mariner, inline 6 approx 1979-1985. I went to start her up today but it wouldn't go. It does turn over however there is no spark on the 4th plug so I bought a new coil and still no spark.
Even though there isnt any spark on that plug am I right to assume that the motor should still run but it would be rough? Or is there a underlining problem connecting it all? Any help would be great? I've uploaded a couple of pics.

 

[racerone]

The motor should still run on 5 cylinders.---------------Swap the 2 powerpack ( cd switch boxes ) and report what happens to spark.---------Those 6 cylinder motors run really nice if they are in good condition.--------How long have you owned this motor ?--------Have you heard it run recently ?

 

[hore1984]

How long have you owned this motor ?--------Have you heard it run recently ?

Thanks for the reply, I have only just brought the boat and was told that it had been sitting for about a year, so I have changed the fuel tank and lines, new fuel/water separator, new fuel filter, new spark plugs and a new number 4 coil (thanks what I thought the problem was). Got a guy coming out tomorrow to remove the carbs and give them a clean also might get a diapharm kit put on the fuel pump. Haven't had chance to swap the switch box yet but will this week.