I only get spark on 1 cylinder on my mercruiser 140. Could it be the spark plug wires? They have been on the boat for at least 3 years. I have replaced everything, Ignition coil, spark plugs, rotor,points, cap,condenser.
Sounds like the wires then. If you get a spark at all, your coil and points and everything are fine. If you had the wrong size cap or rotor then you wouldn't get a spark either (they're round, so everything would behave in the same way).
Another less likely scenario is that or the cam that the contacts follow is worn abnormally and isn't pushing the points together each time. You can manually rotate the engine so that as each lobe on the cam pushed the points together you can check the gap.
