Yes, I thought about spare shear pins already. However, the dealers I spoke with yesterday said there is none used on the Mercury outboard - don't know that I fully understood what they were describing to me - I though they said the prop would slip rather than shear a pin. I will look into this more, as well as a spare prop.
As an aside, I bought a rather expensive big new Honda track-driven snowblower this past winter and promptly broke 2 shear pins (it came supplied with 3 spares). With just one extra shear pin left, and some 18" of snow, you can bet I really watched where I was going from then on! What a way to learn how to use a new machine. I've been buying spare shear pins ever since, and actually just bought several more for it this past week even though I shouldn't need to use them again until next December!
I also have a spare anchor for my driftboat, and never take it with me in the boat - lot of good it'll do me when I might need it fast!
John