Alphas were developed before Bravos. In the old days, Alphas could support 454s in racing if you were careful. Alphas can still support 300HP..again if you will refrain from doing "Hole Shots". If you have more than 300HP a Bravo is the drive of choice.
These days horsepower is rated at the prop shaft. I think around...maybe prior to 1992, horsepower claims were rated at the engine flywheel. An outdrive uses up about 35 HP to make the two 90 degree turns that an outdrive makes before the power gets to the propellor......as opposed to a straight inboard... which transmits ALL the power to the prop. So if you have an engine making 250HP at the flywheel, by the time it gets to the prop you have
about 215 Hp at the prop. Todays power claims are more honest than prior in that the HP claim is now at the PROP...which ultimately is the "real deal".
Defination: Hole Shot: When you start out at idle speed... and then abruptly add FULL THROTTLE to accelerate in the most spectacular mannner. This maneuver adds severe stress to any drive line.
NB