My thoughts without ever seeing, asking or trying to run with one prop is since the inner prop shaft has end play readings of (depending on year /model/manual you read) .001 - .050 in. (0.025-1.27 mm) to 0.001 - 0.012, without the rear propeller tightened down to 60 lb.ft you'll be possibly allowing a lot of in/out/up/down slop to move around possibly damaging the oil seals, the inner prop shaft bearing surfaces, bearing cup and tapered roller bearing, front gear (Gear Backlash) Spline Lash (from Propeller Shaft Spline Lash) could become compromised too.
A loose prop nut on a single prop drive ends up casing some damage to the prop shaft carrier usually starting with an oil leak... Will add that of course the Bravo 3 manual says do not run boat with a loose propeller.
Since the front prop turns to the left, the boat will possibly want to handle or lean more to one side then you're use to seeing but I believe the boat will move along okay.
Since you're buying new/more props, Do you have an old decent smaller rear prop that you could use for the time being? Within reason, matching pitch size don't matter all that much.
Oh and while its always been debatable on open forum, My personal experience is prop timing helps out some too. See page 3E-8 for a how to install them,
http://www.boatfix.com/merc/Techbk/94/94hse3.pdf
If you do decide to run without one prop installed, please be sure to let everyone know how it all turned out for you....:eagerness: Good luck.
