The HBW 100 transmission is, as you know, equipped with forward and reverse rotation capability which Hurth
refers to as position A and B respectively. Hurth recommends that position A be used as the normal "forward" position, because position A allows the power flow to travel directly from the input shaft to the output shaft and not use the extra idler gear
which comes into play with the B position. Thus, position A provides the least power losses, least heat generation and is quieter.
As you mentioned when the transmission is operated in position A, the input shaft and the output shaft have opposite directions of rotation, and when operated in position B the engine crankshaft and the propeller
shaft rotate the same direction. Because your boat is equipped with a LH rotation prop, it is using B position for forward travel. This is not necessarily bad, but Hurth recommends the use of a gear
box cooler if position B is used continuously with more than 25kW (34hp).
It is possible to change the propeller
to a RH rotation and adjust the shift linkage to accommodate, but you should be aware that the forward and reverse gears on this transmission have different reduction ratios. This will be of little consequence if you have the 2:1 ratio(really 1.79/1.86) but it could be significant if you have the 2.72:1 ratio. The 2.72:1 transmission has a 2.72 ratio in position A and 1.86 ratio in position B. This means that a direct swap of propeller size (pitch and diameter) won't be possible for the 2.72 ratio gear. Your prop supplier will have to calculate a new prop size, which isn't the end of the world.
Hope this info is helpful.