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Colin Campbell in his classic book "The Sports Car, It's Design and Performace" (when I first read it in the mid 1960's) said "As a means of finding the weakest point in an engine, supercharging has no equal."
That is as true today as it was then. Turbocharging or supercharging crams more working fluid (air) into an engine. The net effect is that you have more and heat released, and thus higher temperatures in the combustion chamber and exhaust system. This makes it harder on things like exhaust valves and you have to remove more heat from the cylinder head. Exhaust valves run sufficiently hot that a 25 degree F increase in temperature can cut the life in half (stress rupture life at temperatures above 1800 F). The net result is that trying to get too much power from any particular engine will trash it in short order.
Cars are being pushed by fuel mileage regs and that favors a small engine. The customer wants more power, so they hang a turbo on it to get the best of both worlds. That works for the duty cycle you see in cars, but not for boats.
Boats can run at high power for long periods, and if you try to get too much out of it you are not going to see much life. Better to get power from more displacement than trying to boost it with a turbo.
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