I picked up approximately .75 to 1 full knot sailing speed with a Max Prop on a Tayana 37. Had a fixed 3 blade 18" dia.
Best advantage is that you can alter the pitch (underwater adjustmant is a pain) to optimize the rpm / horsepower ouput of the engine.
I thought the Auto Prop. was well overpriced and therefore I went to the Max. Another possibility is a feathering prop from Martec - the Martec couldn''t fit my aperture, ... was the most economical available.
I replaced a 3 blade fixed, 16", on our 34'' with the autoprop and am very impressed. We went from avg. motoring speed of 5.2 @2300 rpm to 6.2. We now run at 1900 to 2000 rpm and maintain 6K. Light wind performance under sail has improved dramatically. It was a little more $ than max. but feel it was worth it to get curved blades.
We have dual max-props on our Prout Escale 39'' catamaran. They have been very good to us, although adjusting the pitch on the older models is quite difficult.
I haven''t seen the large price discrepancies previously reported here between AutoProp and MaxProp. Of the two technologies, the AutoProp is clearly superior since it adjusts its pitch for every speed setting unlike the MaxProp that is just as pitch-limited (once set) as the fixed competition.
Thus, my clear replacement choice is AutoProp, should our MaxProps ever fail. Until then, I''ll enjoy the MaxProps as much as I can.