Max prop on a saildrive
We just got our first boat with a Saildrive. I was reluctant (for the reasons Jack states) but have seen few problems with them on boats I know. One friend has had a Farr 1020 with Saildrive for almost 20 years, no problems and the technology has surely advanced. Granted we sail in cold, less corrosive waters. There is virtually no propwalk on our boat, due to the factors listed above. Backing out of a slip is a pleasure, its like a car, just turn the wheel. The horizontal drive is very efficient - the prop is pushing back, not partially down. The freedom from vibration is very good - no shaft alignment issues.
I agree Max-props have low drag under sail, as do folding props, and they are unsurpassed in reverse. The problem with Max-props is low efficiency in forward, due to the flat blades without twist or cup. Remember we use forward 99%+ of the time. So how much much power do you need to back out of a slip or set a hook? I used a Martec 2 blade folder for years, famous for low power in reverse; maybe I needed a couple hundred more RPM in reverse but so what? We have several friends with Max-props unhappy with fuel efficiency, due in part I suspect to the low efficiency of the flat blades. They do offer the advantage of messing with pitch till it''s right and that may account for the people who swear by them - they finally got the right pitch prop.
We got a 3 blade Flex-0-fold. With a clean bottom our 41'' boat with 55 hp gets 9.5 knots at full throttle. The three blade gives you more margin for balance issues as Jack mentions, and 55 hp is marginal to absorb with a 2 blade. At 2200 RPM we get 8 knots even. We give up some power to a Max-prop in reverse but there is so much surplus it''s never missed. I suspect you''ll like the Saildrive. Keep those zincs up.