Like others have already said, there is something to be said for not running something mechanical like a boat engine at capacity. De-rated motors whether intentionally that way by manufacturer limitation or by operator choices has shown to reflect longer life span on engines and healthier ones at that. Personally, I will gladly take a bigger engine that does not need to run at maximum capacity routinely to accomplish the amount of work I am demanding from it. 6.0 V-8 in my tow rig, I get 12-15 miles per gallon towing my boat but I am never over revving the engine to get the ensemble moving or keep it moving, even going up hill. I can buy a ton of gas for the cost of a drivetrain repair or even worse replacement which was the driving force behind getting a dedicated tow rig to haul our boat around instead of using my wife's daily driver.