Prop Hub Failure?!

[Frstbyte77]

I recently purchased a 77 Searay 220 w/ a 5.8 omc (pos)... got a good deal so i couldn't resist. Anyway it had no outdrive so after some research i located an purchased a used unit. It came with a 14x14 prop.. went out last week and managed to get 25mph, but the motor was revving too high... so i called a few local prop shops and tried to locate a prop w/ better pitch. Unfortunatly, no one had any?! but i was reffered to a guy who recently bought a hole bunch of props and was willin to sell em' . Ended up paying 150$ for a recently redone 14x18 that was spooned and had a nice new brass hub... took the boat out and it ran beautiful, got about 50mph out of it, and it an low rpm it was the perfect speed.. was out all day, on the way home went to get up on a plane and the an half way there the shear pin some how blew up the all the brass around it?! i thought the pins job was to break before the hub? do they make stronger hubs? Could i have done something wrong?... Ive always owned outboard merc's...and this is my first an last omc... please excuse the long story just wanted to cover all the bases.