Have a 1985 50hp mercury that won't fire. Motor was running in July except for starter having a bad bushing in top plate. Disconnected battery and removed starter to try to get it fixed or find a replacement. Put starter back on today and tried to crank motor. Starter spins,motor spins over but there isn't any fire coming to the plugs. Hooked a spark tester to each wire and no spark. Don't see any wires left undone. Any ideas?