I'm not sure I understand what the spark has to do with igniting the air / fuel mixture in a hybrid? Once it's lit... it's lit. I would think any type of strong spark that would make a 1/8" crest would be sufficient to ignite the mixture...?
After all, pressure inside an internal combustion engine is much higher then in a hybrid cannon and many of these coils put out a modest 100k - 150k volts..
I work on propane engines all the time. Cylinder pressure without the explosion is at 90 - 110 psi, then add the the combustion and who knows where you're at... You can open a plug gap to 1/4" and it'll still ignite, hell, I've seen plugs with no gap igniting the mixture.
Anyway... to answer your question. I forget the formula for how many volts are needed to jump a certain size gap, I had a chart somewhere from electronics school but I cant find it. I believe it's somewhere around 75k - 100k volts because it'll jump a good 3/8" gap. I have to plug it into a 110v AC .
Ya, that's my 1996 18' Stingray I/O. I just sold her though. Very nice boat, would pull 3 skiers, pop'em right out of the water. I just bought a 2000 Challenger 20' Sea-Doo jetboat...

Oh sooo sweet! It has a 240hp EFI M2 Jet drive. Haven't even gotten her wet yet and I've got my hands deep into the engine.

(why can't I just leave things alone

)