What would be the best engine and drive

If you believe this then buy your sailboat now. There will always be petrofuel and people willing to use it.

 

That, I am doing, - - But will you be able to afford it in 10 to 15 years time?

 

A Merc HP525EFI, 8.2 litre V8 putting out 525 horsepower, regularly shows up on the Web for $34,000 USD. $65/hp, you *might* get a Bravo 1 drive included in that price if you're lucky, and this is fairly simple as speedboat engines go. A supercharged, 9.1 litre 1075 hp Merc that would be more suited to the stated intentions of the original poster in this thread runs $100k plus drive, there's $93/hp for the engine alone. The $50/hp ballpark will get you a new Merc or Volvo marinized 3.0, 4.3 or 5.0 litre motor, of a design dating to pre-1980 (albeit with modern EFI), and a basic outdrive or gearbox.

None of the marine diesel manufacturers are particularly forthright about their pricing structures- you pretty much have to find a dealer and get an application-specific quote. But $100k for a high-performance, high-speed 500 hp diesel appears to be relatively common. In the smaller sizes, the cost per horsepower can increase dramatically, sometimes as much as $300/hp, if you want a light, high-power diesel with the best of the best in modern computer controls and exotic alloys.

Being able to build your own engines will certainly reduce the cost, Danny. Your own experience is wonderful proof of that. Still, the price difference between a home-rebuilt Chevy 350 and a brand-new, professionally installed 10-cylinder MAN is shockingly huge.

 

Oh I know there is definitely a difference between a 350 and a nice MAN LOL. My issue is that I can't afford that, so I do what I can to make ends meet. You could find Cat diesels, or Deeres, and marinize them, but like you said, there is a difference in pushing a 25' boat and a 40' boat. I guess I shoulda said that "I" would exhaust all means searching for a less expensive route that would achieve your goals before I settled on paying for a brand new drive set up. But if ya got the money, then hell, go for it! I would!

 

So would I, my friend. So would I.
I have very little interest in owning an engine that costs as much as a house!

 

You are doing this the wrong way round. Tell your prop man what you expect from what boat and what weight and speed. He will then give you a choice of props and gearbox ratios and engines with required HP and RPM.

Don't just slap in some motors and some second hand gearboxes then expect the prop man to get you out of the ****.