Engine of choice for 90's Hats

In that size most manufacturers have a choice of 2 or 3 engine makes. 1 will undoubtedly be the preferred. When you get a bit bigger the customer specifies whatever.

Detroit Diesels were the standard, or "base" engine package in the larger Hatt's from the 1990's. The upgrade was sometimes MTU, but the premiul and preferred choice was CAT power. Just look at the resale of these boats and you will see that the CAT powered boats bring significantly more money.
The nineties is the decade that saw the old 2-cycle Detroits fade and give way to four-stroke diesels.

Mid 1990's is still 1990's, so they weren't all DD's. Example: The Hatt 74 came with 12V92's at about 1050hp as the base engine package, then the MTU's with 1150hp, then the top choice was the desirable CAT 3412's at 1350hp. You are right about the MTU's and there is a blue hulled 74 with MTU's that is still on the market probably because people either want the CAT power or the old reliable Detroits. There is about a $200k swing in sales prices from the Detroit powered 74's and the CAT 3412 powered 74's. I learned this last year when I looked at several of these boats in depth with the intent on purchasing one, then I fell for the Fexas 78.

I don't know of any of the bigger Hatt's with an "N" natural engine option in the 1990's. I'm curious, who made a naturally aspirated engine that made enough HP for a big Hatt in the 1990's?

Yes, all the LRC's (42, 48, 58 and 65) were naturals because they were long range cruisers, but they went out of production by 1985. To my knowledge there has not been any naturally aspirated engines in a 60' or larger Hatt from the 1990's. I believe that although most 1990's Hatt's are DD's, any engine choice would be turbocharged.

12V71N's were made quite popular originally in the 1970's Hatt 53 Convertibles, rated at 550hp. They were indestructible, but did not offer the speed that folks demanded more and more as the years passed. By the 1990's, everyone wanted far too much speed for any naturals to produce.

12V71N's would be great for the OP's intended purpose of lugging around at 10-11kts from island to island, but he will not find them in a 1990's Hatt of 60'+. He will have to settle for a much older Hatt. They are all great boats and many of the older ones have been completely refit so an older boat may offer more bang for the buck than a newer one, especially in this market.

Some interesting theorizing in this thread as regards engine choices for the Hatteras brand. From my dozen or so years' experience with a yacht manufacturer building boats similar to Hats, here's the deal:

In the late '70s, General Motors (Detroit Diesel came later), Cats, and Cummins were offered in turbo and naturally aspirated form. A Bertram 31 could be fitted with gas 330 Mercs, GM 4-53Ns (140 HP), Cummins 504Ns (195 HP), or Cat 3160Ns @ 210 HP. Pantropic, the local Cat distributors, hotted up that 3160 with twin dry turbos and called it the 636. Peoria put this into production as the 3208T @ 260 HP.
Lots of choices. As the boats increase in size, the number of choices grew smaller. A 38 Bertram either came with Cat 3208s or Cummins 903s--neither of which were naturally aspirated because of the ongoing horsepower wars and, let's face it: turbocharging = free horsepower.

For the larger boats, Cats & Cummins were too small and by default, GM/Detroit became the engine of choice, with 12V-71TIs becoming the workhorse until the 12V-92TAs @1080 HP pushed the 71-series aside.
You could not, as a customer, "choose" your motors. You were fortunate enough to sometimes have two choices (and if you were smart, you didn't pick the smaller HP of the two for reasons of resale if nothing else). The size of the boat dictated, more or less, which engine would work. We're talking Production boats here...it was tough enough to engineer one engine application to keep costs down.

After a fashion, the four-stroke engines (e.g., MAN) offered better HP/lb. and better fuel economy, plus it seems that DD was falling out of favor with the buyers who began to demand Cat 3412s over the larger Detroit iron. Even very pricey MTUs were offered in the Hat 65C when going faster meant that the 12V-92s became yesterday's lunch.
Too, EPA rules changes dictated that two-stroke diesels would soon be phased out--DD came out with their first-ever 4-stroke with the 60-series in the very late '80s.
I believe the last ever NA engines were Ford Lehmans that saw service in trawlers & motorsailors, plus the odd Cat 3208NA @ 210 HP for the same purpose.

It comes as a shock to some, but marine applications for diesels are but a tiny niche. Trucks are what dictate what the engine boys build. Likely, half the buses in Europe are powered with MANs.

Even if there were, currently, a 12V-71 NA, it could not compete on price with, say, a John Deere inline-six of the same HP.

Speaking of which, Pelagic Dreams--your 60 Hat, at displacement speeds, needs all of 325 HP, which is what drives a Nordhavn 62