Yes indeed you need to be picky! Someone gave you the prop calculator used by Victoria
Propeller Ltd. Use it! Around here, it is what all mechanics use. As you see, it asks you for some basic parameters. In the binder of "Ship's Documents" you carry at your nav-station, you should already have these. If you don't, this is an excellent opportunity to start compiling them.
Here is a basic page of specifications you can simply print out and insert in the binder of
documentation:
MORGAN OUT ISLAND 41 sailboat specifications and details on sailboatdata.com
For BWL, which is not given in the overview, use 11 feet - that'll be justabout right.
Someone spoke of a left-handed
wheel. Whether yours is right- or left-handed will depend on your particular engine
installation, but you gotta know it! Put your tranny in forward
gear, look at the prop shaft or the flange where it comes out of the tranny. Have someone crank the engine a turn or two without actually starting it. Note which way the shaft turns.
If the top-side of the turning shaft would move to your right if you were standing aft of the ship and looking forward, i.e. if so viewed the rotation is CLOCK-WISE, then you need a RIGHT-handed prop. If the topside of the shaft moves to the left, ie. the rotation is COUNTERCLOCK-WISE, you will need a LEFT-handed prop.
Once you determined the right specification for the prop you'll include THAT in your
documentation, right :-)?
Note that at wide open throttle in forward gear you should be able to get 95% or so of RPM (max) specified for your engine. If you can get more, your prop is "too small" or to use the jargon, you are "underpropped". If can cannot get that much, you are "overpropped". Both conditions are deleterious to engine life and, less importantly, to boat performance under
power.
As for losing your prop: Someone goofed! When you were in the yard, did you PERSONALLY inspect the prop
installation and make sure that 1) the taper on the shaft was clean and bright, and the
interior taper in the prop hub likewise? 2) That the key that positions the prop on the shaft was correctly inserted and extended the entire length of the keyway in the hub? 3) that the retainer nut was the "castellated" type, i.e. had slots cut in it through which you insert a "split pin", also often called a "cotter pin", that goes through a hole in the shaft so the nut can't "unscrew" itself?
My position in regard to such important,
safety related tasks is that you should never leave them to "professionals" without monitoring and supervising them closely. :-)
All the best.
TP