What's the right Prop?

[McGillicuddy]

Yeah 1000 lbs hanging 24 or more inches aft is substantial. You're gonna need some help. Regarding stated diameters, are they both Yammie semi-cleavers or what are they? model, diameter & pitch...
Look for easiest to turn, wide diameter, limited cup, stern lifters you can find. This might be a perfect place for powertech MQS props.

Top end and max economy may not be concurrent. I would opt for more economy and lower planing speed. at the cost of a couple of mph. at 45mph I doubt you'll notice. As Bushwacker suggested a stern lifting 4 blade a might be the ticket. Just make sure you're able to wind it up to target top rpm at full load. 14.5 x 17p probably close.