heres a list of prop sizes that fox recommends for the .74

PROPELLERS TO USE:

We recommend that you use only hardwood propellers and stay away from the plastic ones. The reason is, that if you should be so unlucky as to put your hand in the propeller arc, the wood propeller will not hurt you so bad.

Now - about the sizes to use: An 11" Dia x 8" Pitch ranging up to a 14" Dia x 6" Pitch is the practical range. For a 5 ft. sport model we suggest an 11-8 or 11-9 prop. For a 6 or 7 foot model we suggest a 12-6 or 12-7 prop. For an 8 or 9 foot model we suggest a 13-5 or 13-6 prop. 14-4, 14-5 and 14-6 can be used also.

Where quiet operation is important, lean toward the slower running props. Rounding the blade tips also helps.