Re: Turbo charged diesel
I am not familiar with the specific engine in your boat but it sounds like it is a monster physically. There are only 2 ways to get the horsepower up on an engine, spin it faster or put more fuel in. Things like sport bike engines have phenomenal power to size ratios but they also spin over 10,000 rpm. It is possible that you have a very small turbo designed to give you a bit of extra top end or keep within emissions ratings on the top end, this would result in a very large engine with a turbo. Sorry, I just don't know the specific engine.
One of the most popular diesel engines in different applications is the Cummins 6bt of which they offered both naturally aspirated and turbocharged models. The standard naturally aspirated marine version is 120 hp while the turbocharged versions are 250-375 hp (the newer ones with common rail are up to 425). Another example of this might be the Detroit 671 (okay it had a blower but it was really low pressure and it helps with power anyways) which was up to ~190 hp without a turbo and up to ~450 hp with a turbo depending on the year. It really depends on how big of a turbo they put on it and how good of a job they do of heat management and emissions but huge gains are possible.