I have a couple questions, I have an old Merc 850 serial # 7010505. I ordered the service manual for it but still don't know the year. I do know it's Canadian. Also it wouldn't start and I discovered a cracked ignition rotor, which I replaced along with the distributor disc, but I still don't seem to get a spark. I did see one spark while cranking it trying to troubleshoot, but nothing consistent, and the way the manual shows to test the other ignition parts, eg. trigger, switch box, coil, all involve a spare trigger, which I do not have. Are there any other ways to test these components to see what I nee to replace?