What can go wrong WILL go wrong. I only had the one key and it was really looking past it. Not visible by thumbnail image is a hairline crack across the blade; a victim of too many bendings from body bumps and slams (the engine control panel and ignition switch is located in the companionway and the key protrudes) It might eventually break off (in the switch!) or go missing. Either way, SOL.

I took the original to a locksmith or two to see about cutting a new one. Out of the zillion types onhand, none could procure a suitable blank. Yanmar no longer provides for replacement keys. Solution: Order the entire switch. Comes with an extra to boot.