Just from my experience .  I have a 1:1 transmission and switched over to a 14" 7 sailor prop over a 3 blade mouse ear michigan 13.5" 6 and found the sailor does a better job under motor, so for me the old thought of the three is better than 2 did not prove correct.

Gary,

Norm is right.  Propeller theory states that 1 blade is the best (like a sculling oar), but we have yet to figure out the balance and vibration issues that come along with it.  3 blades create more of a "stirring" (wasted energy) than propulsion/thrust, hence a 2 blade performs more efficiently.  We are also constrained by the physical space.  A 3 blade can be smaller and perform, but it comes at a cost with drag and lower efficiency.  It is always a compromise. 

Tyler

      Oh horse poop! If this were true every fisherman in my harbor with a displacement style full keel boat would be running a 2 blade instead of the 3 or 4 blade they are running.Sometimes a little common sense goes a long way. I run a campbell 3 blade and have tried a w32 with a two blade. The 2 blade has the advantage under sail but not motoring.

                                                                        Lee

Life is short folks -- let's be gentle on one another -- differences of opinion are just fine -- labeling an opinion/person are not so fine - you are allowed to edit posts after you have Posted if needed.

Gary: you are correct as well.  Not changing the diameter and pitch of the prop, would advocate a 3 blade provide more thrust, but at a lower efficiency of energy transfer.  Again it is a trade off, and I'll will leave it as that.

As I originally posted, I was hoping not to open a can of worms.  I got the feedback originally desired, and thanks to those whom contributed on all sides of the argument.

TJB