Hi Brian, I use a 13/6 APC turning 8100 to 8400 rpm's on my merco and she runs and flys great. Lap time is 5.2 seconds on 60 foot lines. A Merco with a Magnum is a great combination. Mine will do the pattern using a 6 1/2 ounce tank. Mine weighs out at 64 ounces. Have a great day, Gary