As marc pointed out, positive displacement superchargers put out very close to max boost at any speed over idle. If they put out 10psi at 6000, then they'll put out very close to 10psi at 1500rpm - not the relationship you expressed. It is th emechanical nature of positive displacement blowers (and why ther have that name) that they pump a given volume of air with each rotation ( up to the pressure within their design spec). Be aware that we are talking about boost pressure with the throttle open (because otherwise you aren't reading what the compressor is capable of, only what it is doing under part throttle conditions).
And Honda did not have the first production 4-valve per cylinder engine (I know you said they were only "among the first"). Chevrolet had one in 1974 with the Cosworth Vega. If you want to exclude the Cosworth from the running due to its limited production status, then Mercedes beat Honda with the 1983 190E. This doesn't even mention the other early 70's cars like Jensen Healys and such. And Honda doesn't "do" production 5-valve motors - only a few race ones. And, also, Honda has no current DOHC marine motors, only SOHC. Suzuki is the tech leader in gizmos on outboards...
Honda trailed Mercedes in variable valve timing, as well, coming in 2 years behind the 2001 SL, and moving thru the entire range of Benz V8's by 1992.
And variable valve lift? Cadillac, 1981 (yeah, I know it didn't work very well).
(ALL of these advances were pioneered by aircraft and racing engine gurus in the 1915 to 1945 range)
What's different about my discussion of Honda (and others') new marine motors versus your mention of BMW? Simple. I am talking about motors designed from the ground up for a marine environment, not a marinized high revving performance automobile. You were extolling the virtues of the Bimmer, specifically. You didn't say "Wow this Bimmer motor AND THE NEW 4 STROKE OUTBOARDS would be great new boat motors". There is where I claim to see a difference. If you were expecting us to "fill in the blanks there" then I regret that I was not insightful enough to understand to do so.
496 won't cut it on a patrol boat, eh? Wouldn't by any chance be a misapplication of the motor would it? How do you feel that your BMW motor would work there? Or maybe you feel that an S2000 motor would live at it's power peak (7700 rpm) for 50 hours. My guess is that your patrol boat has improperly sized heat exchangers and/or propping for the application.
I'm confident you are familiar with the output classifications for diesel engines. You of all people, should recognize that a pleasure craft (class E) motor is tuned to provide higher power output, albeit for shorter WOT periods with adequate "resting time". A Class C motor is designed from the same basic envelope to provide a lesser power output but at higher percentages of WOT operation. A Class A diesel is designed to primarily run full throttle for months at a time without being shut off or unloaded.
The patrol boat application you speak of is definitely NOT a Class E Pleasure Craft application. It MIGHT be a Class C "Maximum Continuous" Application. Or It might be a Class B "Heavy Duty" Application. It is DEFINITELY NOT a Class E High Performance Pleasure Craft application.
The 496 you make mention of is a Class E crossreference. Sorry if it isn't holding up. Somebody needs to pony up for some true Commercial Duty motors for those patrol boats.
And Diesels are indeed my preferred choice of power in a heavy boat. But you gotta pay for them and the marine pleasurecraft industry has learned by experience that the consumer will choose the cheaper motor every time when the top speeds are comparable - and it doesn't matter if its lifespan is drastically reduced over the more expensive choice.
I guess it's the same reason China is doing so well in the world marketplace. Quality and longevity be damned - I want the cheaper one.
I still say that the mass-market American performance boating community won't pay a penny more for something "exotic and better" unless it will stomp the holy britches off an HP500EFI. And I don't think there's any current basis on the market for a marine motor that can outwrangle the blue Merc (or for the money, the 496, unless it is grossly misapplied).