can I get any ideas about prop size?

[fishez4alivin]

What it was was my A/V plate was too low, so i raised the engine and can get 5800 with the 14 1/4 x 15 cupped.....i will use this prop when im carrying a large load, and switch to the 14 1/2 x 19 when by myself, which is rare. I have the boat loaded with custom tank where the enclosed head should be, and carry as much as 100 gals of fuel if i go offshore, that is why i need the small pitch, also carry a 50 gal kodiak tank along with the corner tank i load for chumming. I get about 43 knots now with the 14 1/4x15