what prop is he using?

Good luck with your Checkmate. It's a great boat that will surely deliver bigtime with fun factor. My first performance boat was a '96 253 Convincor with a 454 mag - 385 hp. I switched back and forth between a 25" mirage plus and a 23" mirage plus ... both did a great job ... I actually preferred the 25" which gave a bit more at the top end without sacrificing midrange performance. I believe you have the right prop for the 502 ... it should easily max out the boat's potential. As I recall you should see high 60's to 70 mph on the right day. Handling is very predictable, and the ride felt bigger than a 25' boat. Best of all, you can run all day without burning up a lot of gas ... that will change dramatically by the time you get into your 3rd or 4th moneypit.