Same here, I don't know how I ended up being the most mechanically inclined of my friends. I get to work on the family fleet, which isn't so bad as they are all first owner cars and well taken care of, and nice cars to boot. But when I spend a couple hours tearing apart a carb on a boat and putting it back together (and burning and blistering my back in the sun) and getting paid in beer, its okay. When a guy at work starts asking my why his Blazer won't start and he's trying to get a diagnosis out of me on the spot, that's not so cool. When I get introduced to someone as "Brian, he's my mechanic" and I hear "Oh, really, my car is making this funny noise" I just want to slap someone. The bad part isn't being introduced as a mechanic, its when someone immediately thinks I can just say their car has such 'n such a problem and that I will give up a Saturday to help someone I just met. I'm a nice guy and all but that starts crossing lines for me. And all the urgent stuff is bad, being a mechanic is not my job, I have other things to do in the course of a day.
That being said, I like working on things, but there's a point too far.