Must be some underlying problem for it to break again.........?
Not sure what, but I'd get it all checked over before throwing more money at it 
bit late for that
Here is what it looks like .......
Thee other side is a Smaller crack
Not sure if this picture is of your actual mount but in the above picture the engine mount failure could possibly be the result of improper installation, just look how out of alignment the mount is! It's completely jagged. The bolt should sit centred on the top mount as to cover up the hole. Chances are because it's so far out of alignment the bushes aren't working and instead you have metal on metal contact.
Power would definitely not be the reason for the mounts failure in the above case. I've had mates run gt2871r on standard mounts for a whole season without such problems.
