Can someone help my understand how distributor and crank position sensor relates?

[Mxylplyx]

So I ended up stranded in the lake this past weekend with a dead engine that had no spark to the main plug at the distributor. This is a mercury 350. The boat is with a mechanic now, but I an trying to figure out all the possible reasons for this. The simplest explanation would be a faulty ignition kill switch or frayed wire leading to it that is grounding out the spark. If that's not it, a guy here at work thinks it would be the crank position sensor failing to fire. He called it the "stater". Could someone here explain to me how a crank position sensor relates to a distributor on a carburated engine? I figured that once a distributor pin is correctly aligned with the crank, it would eliminate the need for a crank sensor, and the distributor rotor would handle the timing. Having a crank sensor makes perfect sense to me for a fuel injected engine, which this is not. The guy was a mechanic for 8 years, so I have little reason to doubt him.

Could someone please school me? TIA.

 

[exdeath]

Does it have electronic ignition instead of mechanical points? If so, you need some sort of crank angle position info to trigger the coil collapse regardless of distributor position.

Electronic ignition with distributor is as follows:

Crank or cam angle position sensor and a power transistor (ignition module) is required to trigger the actual field collapse of the primary coil winding that generates the high voltage spark source in the first place. (handled by mechanical switch called points in full mechanical ignition).

Mechanical distributor then routes the high voltage discharge from the single secondary coil to the appropriate cylinder. So the rotor may be mechanically lined up with the right cylinder, but the electronics are what actually detect crank position and fire off the spark.

The only reason you have a distributor in a electronic ignition system is because you only have one coil. Typically you don't have a direct crank position sensor in this case, but a cam position sensor and reluctor wheel within the distributor housing in the same location that would normally house points, along with wires coming out of the distributor base connecting to the ignition module.

 

[Mxylplyx]

Does it have electronic ignition instead of mechanical points? If so, you need some sort of crank angle position info to trigger the coil collapse regardless of distributor position.

Electronic ignition with distributor is as follows:

Crank or cam angle position sensor and a power transistor (ignition module) is required to trigger the actual field collapse of the primary coil winding that generates the high voltage spark source in the first place. (handled by mechanical switch called points in full mechanical ignition).

Mechanical distributor then routes the high voltage discharge from the single secondary coil to the appropriate cylinder. So the rotor may be mechanically lined up with the right cylinder, but the electronics are what actually detect crank position and fire off the spark.

The only reason you have a distributor in a electronic ignition system is because you only have one coil.

I think I understand. I wasn't thinking about where the actual coil was that generates the spark, so forgot that that needed a timing mechanism as well.