Mercury 200 series 20hp keikhaifer weak spark?

Hello, new to me old outboard that has what I beleive is weak spark..... Point are cleaned and gapped, condensers tested to spec .3 uf. Coils show 6-7k ohms from primary to end of spark boot. Kill switch completely taken out of the wiring loop to remove from the equation..I have disassembled and reassembled probably the magneto probably 4 times, regapping and cleaning points. Spark plug test light does light up and visible with garage door closed, but not bright enough flash to see in daylight. Should I be seeing very bright flash from spark bulb or are these old systems generally low voltage.

Does spark jump a gap of 5/16", yes or no?

racerone said:

Does spark jump a gap of 5/16", yes or no?

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No sir, I physically have to touch the electrode to block bolt to see any kind of spark.

topfli8979 said:

Hello, new to me old outboard that has what I beleive is weak spark..... Point are cleaned and gapped, condensers tested to spec .3 uf. Coils show 6-7k ohms from primary to end of spark boot. Kill switch completely taken out of the wiring loop to remove from the equation..I have disassembled and reassembled probably the magneto probably 4 times, regapping and cleaning points. Spark plug test light does light up and visible with garage door closed, but not bright enough flash to see in daylight. Should I be seeing very bright flash from spark bulb or are these old systems generally low voltage.

Click to expand...

topfli8979 said:

Hello, new to me old outboard that has what I beleive is weak spark..... Point are cleaned and gapped, condensers tested to spec .3 uf. Coils show 6-7k ohms from primary to end of spark boot. Kill switch completely taken out of the wiring loop to remove from the equation..I have disassembled and reassembled probably the magneto probably 4 times, regapping and cleaning points. Spark plug test light does light up and visible with garage door closed, but not bright enough flash to see in daylight. Should I be seeing very bright flash from spark bulb or are these old systems generally low voltage.

Click to expand...

iboats Mercury | Mercury 200 series 20hp keikhaifer weak spark?

Weak spark on both leads or just one? That tells you a lot. Here's what I'd check, in this order:

1. Pull both plugs. The spec is NGK DCPR6E gapped at 0.9 mm (0.035 in). Fouled, worn or rounded plugs, or a wrong gap, can pass for weak spark. Replace them if in doubt.
2. Measure secondary resistance across the plug cap terminals with the leads and caps still attached. It should read 16.8 to 20.2 kΩ. Anything above that means the coil or lead is going.
3. If it reads high, take the caps off and measure each lead on its own. The spec is 3.0 to 7.5 kΩ. If a lead is over, replace it. If the leads are fine, the coil is the problem.
4. Check the crank position sensor. It should read 148 to 222 Ω. If it's out, the trigger signal is weak and you get a weak spark.
5. If everything above passes, check primary coil resistance, which should be 0.26 to 0.35 Ω.

Is the weak spark on both cylinders or just one?

OutboardBuddy this one has old school magneto ignition, no crank position sensor.
The system contains of two ignition coils , two points and two condensers.
Topflie8979 ignition coils should read 5-8KOhm at secondary side, prime side 0,5-1,5 Ohm.
Clean the points and gap them to 020 in and check for spark.
It should jump at least 1/4 in or more in atmosphere.
Compression should be at 100 PSI or more at both cylinder.

Nordin said:

OutboardBuddy this one has old school magneto ignition, no crank position sensor.
The system contains of two ignition coils , two points and two condensers.
Topflie8979 ignition coils should read 5-8KOhm at secondary side, prime side 0,5-1,5 Ohm.
Clean the points and gap them to 020 in and check for spark.
It should jump at least 1/4 in or more in atmosphere.
Compression should be at 100 PSI or more at both cylinder.

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Thank you sir, all those measurements are in spec. I did find continuity from both primary wires to the block.... i suppose that is probably my issue?

I see a new set of coils in your future. New condensers as well.

Topflie8979 one side of the coil should be connected to ground.
If the coil has one thin wire (prime side) and one thick wire (HT wire to the spark plug, secondary side) you measure the prime side at the thin wire to the iron core and secondary side from HT wire and the iron core.
Remember that the prime side has a very low resistance so the prime side resistance is just about 1/5-8000 of the secondary side.
It does not matter if you measure the secondary from HT wire to prime side wire or the iron core.
One thing that is hard to measure is if the prime side winding is shorted.
The VOM has to be very good to measure a shorted winding vs a good winding as the prime winding should have 0,5-1,5 Ohm that is pretty close to a short cut.