Here is some NY Boat Show Mercury propaganda for 2012 - Quoted off another website.
"Visit the Javits Convention Center on 11th avenue in New York City during the boat show to see Mercruiser’s 8.2 engines that come in 380 Hp, 430 Hp H O, 525 Hp EFI, and 700 Hp SCi variations, among the other engines on display, although not all engines are guaranteed to be at the boat show, in their booth (C-18) and installed in boats on the boat show N Y convention center exhibit floor.
These engines are based on at least two chevy engine blocks with various heads to develop their reliable marine horse power at these levels. The 380 Hp is the one that is popular in a cabin cruiser and bigger family bow riders. Its full throttle rpm range is 4,400 – 4,800 rpm and has a cam and valve train that works best for those kind of rpms. The peak power has been dyno’d at 4,200 rpm before it starts to fall off and the 430 Hp H O version exchanges some low end power compared to the 380 Hp for more clearly power over 4,000 rpm that then peaks at 4,700 – 4,800 rpm. The full throttle rpm range for the 430 Hp H O is put at 4,600 – 5,200 rpm.
A 380 Hp engine will best a 430 Hp power boat up to about 4,000 rpm, where the 430 Hp then really pulls ahead.
XXXXXX has done a sea trial with each of these engines, and in a 7,000 lb type boat it proved hard to tell the difference between them in a pleasure boat application.
Mercury Marine uses its Merc Racing division to sell the 525 Hp EFI bumps up the power and the full throttle rpm to 4,800 – 5,200 rpm. They add even more changes to the engine parts like a different fuel injection system AND a 3.3 liter supercharger to get a rating of 700 Hp at the same full throttle rpm range of 4,800 – 5,200 rpms.
All of these 502 cu. in. (8.2 litre) engines have a bore of 4.47 inches with a 4 inch stroke. "