Hey QM,
Thanks for joining in with that tip.
I'll admit I never examined the sprocket shaft to discern a groove.  But since I never completely removed the shaft,  I don't believe it turned out of position.  The set screw seemed to hold over the weekend tour.  
But certainly something to watch for in the future.  I never woulda known about the set screw - shaft groove.
I did mark the chain link where the center sprocket tooth (wider one) needs to return.  Otherwise, that would throw the whole drive off.
And Kepnutz - 
Thanks for the heads-up on the super glue mast fix.  I'll try that first 
 
Great pix of the day!  I'm guessing you're riding tandem stern 

   Or a good camera-in-the-stern setup.
I'd share a pic or 2 of the Land of Sky Blue Waters (of Hamm's - the Beer refreshing fame) in MN,  but not sure how to attach to this forum.
Til the next "event",
-Mett