Hi Skip,
I believe we met at the SPA contest in Prattville, AL last month. I believe (based on our conversation) that you just need a new battery pack (one that will hold 3.7 volts/cell under a 60-65 amp load)...... and a different prop. APC makes a 15x 13.5 (3 blade) that should do nicely.
Another option would be a pack like you have with 1 more cell (7s). If you are using 10C cells, then 7S would give you about 1100 watts with a 15x10.
As light as your setup is now, the 7S option (with 10C cells) might be the least expensive way to go. Will your ESC handle 7S ?
Ed