No spark, is it coil or shift cutout switch

[Why2phy]

Mercruiser 3.0.
First time out in the water this year, engine started great, one lap around the lake and suddenly engine stopped. Engine does crank, but won’t start due to lack of spark.

12V present at the coil, but no spark at the distributor cap.
Brand new distributor cap, plugs and ignition module. Disconnected all wires at the tachometer, including gray wire coming from coil.

What’s left? Coil itself and the shift cutout switch?

I’m not very mechanically inclined and had help from a neighbour to diagnose for spark. Coil seems easy enough to swap out, but is there an easy way to test out the shift interrupt switch? The switch has purple wire and white/green to the distributor module.

 

[dubs283]

Lanyard/operator presence switch perhaps?

Coils rarely fail completely, however it is possible. A continuity test between primaries and primary/secondary will tell you much of the health of your coil

 

[Eric 3.7LX Alpha 1]

Engine serial number? The 3.0 was made for a lot of years...
Here... read this: https://forums.iboats.com/threads/ignition-coil-mercruiser-3-0-l.647254/
and then this one: https://forums.iboats.com/threads/no-spark-mercruiser-3-0.306909/

Your not the first 3.0 owner to lose spark and ask for help. These will save you and us some time.

 

[Why2phy]

Engine serial: 0L02…
Coil was changed and still no spark.

I’m about to take it to the shop, but I did want to get a better understanding of the shift interrupt switch.

The switch is connected to both purple wire and the wht/grn going to the dist module.

With a multimeter, I checked connectivity on the two wires to the switch. The connection is open but when I manually press the button, I have connection.

When in neutral, ie, trying to start the engine the button on the switch would not be pressed. So what should I get on the wht/grn wire at the distributor module when cranking? Does the switch simply let the 12v thru to the wht/grn when butter j is pressed and GND otherwise ?

 

[dubs283]

When in neutral, ie, trying to start the engine the button on the switch would not be pressed. So what should I get on the wht/grn wire at the distributor module when cranking? Does the switch simply let the 12v thru to the wht/grn when butter j is pressed and GND otherwise ?

You've done some decent troubleshooting thus far, sounds like the shift interrupt switch itself is good.

Check out the stickies at the top of forum page. Good info about your setup and a great troubleshooting guide for your thunderbolt ignition system