1999 5.0gl won't start...weak spark?

M

mikeneal

Senior Chief Petty Officer
Joined
Jan 28, 2004
Messages
710
I have a 1999 50.GL 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.
 
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ken226

Cadet
Joined
Apr 25, 2010
Messages
27
Re: 1999 5.0gl won't start...weak spark?

mikeneal said:
I have a 1999 50.GL 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.
Click to expand...

Is your engine carbed or EFI?

Perhaps the idle circuit or accelerator pump on your carb has a worn seal, rotted gasket or something.
You could drape a gas soaked rag over the air intake and crank it, see if it fires or just keeps cranking.

If it fires with the gas rag, youll know for sure its a fueling issue and not a spark issue, if it just keeps cranking with the gas rag, you'll know you need a new coil/points/ etc.

The old gas rag trick is a hundred years old, but always gives a quick diagnosis.

BTW, if your engine is prone to backfiring through the carb, don't do the gasrag thing :)
 
M

mikeneal

Senior Chief Petty Officer
Joined
Jan 28, 2004
Messages
710
Re: 1999 5.0gl won't start...weak spark?

It is getting good fuel and I replaced cap and rotor. ( they were gross looking). Spark looks somewhat better . Now wondering if the plugs are fouled, they are about two years and 150 hrs old so might try new plugs next.
 
M

mikeneal

Senior Chief Petty Officer
Joined
Jan 28, 2004
Messages
710
Re: 1999 5.0gl won't start...weak spark?

I forgot to post update. Replaced plugs and no change. So with mirror examined coil and discovered it might have been leaking. The steel can rusted and I replaced the coil and fired right up. Not sure why both the primary and secondary side measured within specifications (ohm) but regardless the new coil fixed it. Ran the boat last weekend and ran fine all day.
 
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