I would second the information from Maine (and Stu).The only way you "overload" an engine is with the wrong sized/pitched prop. This can and does happen with two blade props as well as three blade.
Any prop, regardless of blades, should allow the engine to turn max rated RPM at max throttle in smooth water with a clean bottom. If your motor can't attain max RPM then it is over loaded or over propped.
Universal/Westerbeke will deny warranty coverage if you are over-propped..
Since buying our boat in '94, we have used the orig. two-blade fixed, a two-blade featherer for a decade, and now for a couple seasons, a three-blade fixed.
Best for sailing by far is the feathering prop. Best for motoring, By Far, is the fixed three-blade.
If you can live with the speed loss under sail (and we have, about a full knot, so far...) the three blade is waaaaay superior.
The prior feathering or fixed 2-blade designs routinely lost a knot or two against a chop.
So my SWAG is that "there's no substitute for blade area".
Out there in the future, as soon as we find a winning Lotto ticket, we will change to a three--blade feathering prop!
Loren
(M25XP Universal)