I get what u say. I take back the comment of the 550 having a turbo. I knew it was superchgr, just a slip in thought stream.
But, what I mean is, at any elevation, all other things being equal, with forced induction you're always going to retain more power at higher elevations. If you cram in more air, you will have more oxygen available to burn more fuel and generate more power. A forced induction enhanced engine should theoretically retain more efficiency as the elevation increases than a naturally aspirated one. I just don't think you get the bang for the buck in the 440 that you would if you could somehow bolt a turbo onto that thing. I'm not saying you don't get any extra power. I'm not mechanically savvy, I'm just questioning how much benefit you would gain for 8k$. Do you gain just as much "torque equivalent" if you would just switch to a lower pitch prop and sacrifice some speed rather than spend 8k$ for a marginal benefit? I dunno. I wish someone would run the numbers. It would be an interesting project. Not sure how you Dyno a boat, but I'm sure there are ways.
BTW, on that subject. Why hasn't anyone ever commented on easy ways to get more air in that doesn't cost a fortune. A high flow air filter and larger air intake e.g. Should not have to mess with ECU and it's a bolt on mod. Should not void warranty, and if you ever need warranty work and you're concerned, just remove it and bolt on the old one. It's just a car engine. It's one way to get more air in without spending 8k. I'm sure someone here is knowledgeable and can provide some info. I'm just curious. I have no idea how feasible this is. Room in engine compartment a problem?