BHP = torque (ft/lbs) x rpm / 5250

If a 2 stroke delivers more torque - why do they need to rev higher to produce the requisite horsepower to suit the engine load (created by the propeller)?

It would appear that the original question has worked. For most people there is very little practical difference - it is mostly personal preference based on the sound. The exeptions being true 3d (4 stroke) - or genuine top end speed (2 stroke) otherwise it is probably much of a muchness. -

1 lb of fuel will only contain a set amount of potential energy - it's how efficiently the engine transfers that into kinetic energy that makes the difference. - This is why, displacement for displacement, different engines have different power outputs - it's all about engine efficiency which is controlled by many factors.


BTW - BMEP is controlled by a large number of factors - most of which are to do with engine design - I would just about guarantee that, size for size and cycle for cycle, an older style of engine will produce a lower BMEP than one with later more efficient designs (Schneurle porting for instance). this also applies to combustion chamber design, valve timing atc and is a fascinating science all of it very own.