No spark out of distributor - Mercruiser 140 I/O

[Riflejake]

Hi all,

First boat here, not too knowledgeable about Mercruisers but making do.

Boat hasn’t ran in 3 years, and I’ve been able to narrow it down to no spark out of the distributor.

When cranking, I’m able to ground the wire coming out of the coil and get spark. If I try and do the same coming out of the dist and grounding a spark plug, no joy.

So far I’ve replaced the following:
Dist cap, rotor, points (gapped properly) condenser, plug wires, and even the wire leading from coil to the pointe, and still nothing.

I did attempt to replace the coil, but the new one had an internal resistor and the old one said you use resisted wire? Not sure if I can “double” up like that or not.

Things I haven’t tried: removing all wires except points from the negative term on the coil. Any other suggested next steps appreciated.

 

[alldodge]

Points Dizzy, so points just open and close. When they close this grounds the Negative side of coil which causes spark. Neg side of coil is connected to points and maybe Gray Tachometer wire

Clarify if I missed something

I’m able to ground the wire coming out of the coil and get spark.

You can ground the Neg side of coil and get a spark

If I try and do the same coming out of the dist and grounding a spark plug, no joy

You can ground the points wire (must open points first) and there is no spark

 

[Riflejake]

Points Dizzy, so points just open and close. When they close this grounds the Negative side of coil which causes spark. Neg side of coil is connected to points and maybe Gray Tachometer wire

Clarify if I missed something


You can ground the Neg side of coil and get a spark


You can ground the points wire (must open points first) and there is no spark

Correct, and I can also ground the lead wire coming out of the coil, into the dist cap, and get spark.

Unsure about the second part. I can take a spark plug wire, attempt to ground, and nothing

 

[alldodge]

Grounding any spark plug or coil wire should not give you spark. Only when power is connected to + side of coil and the - side is grounded should there be a spark from the coil tower

Every time the - side wire is ungrounded and regrounded there should be a spark, BUT this will only happen IF the points are open.

To check to see if points are set correctly, loosen Dizzy hold down bolt so Dizzy can be turned by hand. Remove Dizzy cap and then look at the points. Turn key ON and then rotate Dizzy so you can see the points open and then close. Each time it opens and closes there should be a spark from the coil

 

[alldodge]

 

[Riflejake]

Grounding any spark plug or coil wire should not give you spark. Only when power is connected to + side of coil and the - side is grounded should there be a spark from the coil tower

Every time the - side wire is ungrounded and regrounded there should be a spark, BUT this will only happen IF the points are open.

To check to see if points are set correctly, loosen Dizzy hold down bolt so Dizzy can be turned by hand. Remove Dizzy cap and then look at the points. Turn key ON and then rotate Dizzy so you can see the points open and then close. Each time it opens and closes there should be a spark from the coil

Replaced points with Pertronix igniter and it fired right up. A little loud, but she is running and gets in gear. Pressure, temp, everything looks great. Time to gut the interior

 

[Scott06]

Replaced points with Pertronix igniter and it fired right up. A little loud, but she is running and gets in gear. Pressure, temp, everything looks great. Time to gut the interior

3.0 s are always loud. Id swear on the trailer my 3.0 in my previous boat was louder than the 5.0 in my current boat

id hang onto your points as both on here and the muscle car forums you tend to see a fair amount of pertronix failures. If you cleaned points and set dwell they would probably get you out of a jam.