No spark on one cylinder,need advice

I have a 3cyl 70hp merc.1983.with no spark on one cyl.I have a CDI outboard ignition troubleshooting book and a DVA adapter and have come up with the following test results but can come to no conclusion.Any advise would be appreciated.Resistance on trigger wires disconnected,Br 1150 White 1220 Violet 1228 to Black and white wire.Resistance on trigger wires to engine ground while connected Brown 15k ohms White 15k ohms Violet 15k ohms. DVA readings at cranking speed connected . from black and white to Brown 5.7 White 5.9 Violet 5.2 .. Same test wires disconnected Brown8.5 WHITE 10.6 Violet 7.6 ..I switched the coils around but the same cylinder still no spark.I tested with a spark tester set at 7/16inch and the two cyl that fire have good spark. replaced secondary wires.Took apart and cleaned all grounds and connections.Checked insulation on all wire,all good,no shorts.Took yellow wire off rectifier ,still no spark one cyl.Don,t know much about these ign systems ,leaning toward switch box,any advise..Thanks.

Re: No spark on one cylinder,need advice

Looks that way....

Re: No spark on one cylinder,need advice

switch coil positive from one cylinder to another. see if spark moves. if it does good way to test switch box and coil.. simple way to test with out special tools.

Re: No spark on one cylinder,need advice

Thanks Water World , I ended up putting on a new switch box and am firing on all three again.I will remember your advice ,sometimes the simplest ways are the best and as you say test switch box and coils at same time. Faztbullit's advice nudged me into the new switch box a couple of weeks ago,Put the boat in the water after installation and it performed well.I tried to get a CDI switchbox but non available until next april so I purchased a Sierra switchbox ,does anyone now if it will be as durable as the CDI.