Max prop on a saildrive
Let''s try to get back to your original issues.
Selecting a feathering prop will provide less drag when sailing (over a conventional fixed prop of the same # of blades and diameter). Unlike a folding prop, a feathering prop should provide stronger backing power. For a given hull, a saildrive should provide less prop wash than conventional running gear because the turning moment of the prop is closer to the CLR of the hull/keel (even tho'' a conventional shaft does incline the thrust a bit, as Jeff mentions). So...so far that seems to justify your engine choice and interest in a feathering prop.
However, I''m not convinced the MaxProp product (which I now use and like very much) is the optimum choice for a saildrive installation. I''d talk with your builder, your boat''s designer and/or the prop manufacturers, trying to distill out which feathering props were initially designed for saildrive systems, which after all can present some very different issues. Look at how close that bevel gearing is to the prop: which props will impose the least off-balance loading should one blade heavily foul or get nicked, e.g. Which prop most easily permits anode replacement while in the water, given that otherwise your sail leg serves as the anode? I can see some variables in here that would weigh heavily on my choice of prop product.
One (unsolicited) comment: you''ve chosen an engine installation that brings some significant compromises, just to avoid a bit of prop walk. If it isn''t too late to order the boat with the conventional engine choice, I''d encourage you to rethink the choice...