He only managed a 1-under 70 in Sunday's final round and won the event at 15-under 269.
David Mathis (65) and Jon Mills (70) shared second place at minus-14.
Kelly Grunewald and Jeff Klauk both shot rounds of 4-under 67 on Sunday to tie for fourth place at 10-under 274. Grunewald moved from 76th on the money list into the top 60 and will have a place in the field next week at the Nationwide Tour Championship.
Due to weather problems on Friday, the second round was completed on Saturday. The final group hit their tee shots of round three on Saturday before the horn sounded ending play due to darkness, so Sunday was essentially a 36-hole finale.
'Today was a long day,' admitted Turnesa. 'It wears on you but when it is time to play golf you have to be ready to play golf. I did that this week and I couldn't be happier.'
Turnesa leapt to 13th on the money list. With the top 25 after next week getting their PGA TOUR cards for 2008, Turnesa has assured himself of a spot on tour next year.
'It feels great to lock up my card,' said Turnesa 'I've known for weeks that if I won I was going to the PGA TOUR. You can't help but think about those things when you're out there.'
Turnesa certainly made things interesting on the last hole at Miccosukee Golf & Country Club. He held a two-shot lead over Mathis and Mills, but hit his drive into the water.
After a penalty drop, Turnesa hit his third into the front, greenside bunker. He blasted out 5 feet past the cup and left himself a tester for the winning bogey.
Before that putt, Mills had close to 15 feet to reach 15-under par. He missed that and now the pressure was on Turnesa. He had to make his putt to avoid a playoff and he did just that.
'I don't think playing 36 holes affected me but the fact that I was playing the 72nd hole may have,' said Turnesa. 'I was really nervous. But it is great to come out on top.'
Mathis may not have made it to the winner's circle, but he did pick up enough money to get into the field next week.
Patrick Sheehan (67) and David Hearn (71) tied for sixth place at minus-9. Roger Tambellini and Kevin Johnson both posted rounds of 2-under 69 and shared eighth at 8-under par.