I have a 1999 Volvo Penta 5.0GL and due to life circumstances it doesn't get much love ( hadn't been in the water in over 3 months) . I went to start it and won't run over, clicked only. Checked batteries me voltage was good. Started cleaning connections and found high resistance at ignition switch. WD40 and cycled it a lot and not turns over good now but wouldnt fire. Occasionally will start or chug when starter is engagueged so I suspected kill switch circuit. Cleaned and checked circuit.a md by-passed with +12v to coil from fully charged battery. Occasionally will start and then will run fine on hose for long periods of time . If I shut off most of the time won't re-start. Measured coil resistances and they seem within spec. When I look at spark at cylinder with new plug spark seems weak and yellowish but honestly dunno what it typically looked like. Cap, rotor and tune up is about a year and 50 hrs ago. Boat runs good when it starts so I think I can rule out fuel, and fuel system. Seems like a weak spark but shouldn't a bypass to coil take the boat wiring out of equation? Sorry for long post.