I don't know how to bench test a coil but if it's on the boat. Pull the coil wire and hold it near ground to see if it sparks. If no spark, Take a test light and touch the pos side of coil w/key on, testlite should lite up. if it does, go to neg side of coil and touch testlite to it while cranking and see if the light pulsates. I think you can take it to checker or autozone and have it tested. Budlight