Hi John,
You seem to be having a real time trying to get the information you want. Having heard from the two who did respond (and it wasn't the numbers you were hoping for), leads me to think you may have reached the limit of potential research that can be gleaned here. Sounds like you need to take the next step: get out on one of these boats to determine if it will do what you want.
When we were in the search for our boat, finding a C-Dory to even look at in deep south Texas didn't pan out. Jeff Messmer (then at the C-Dory factory) said, "You need to come to where the boats are..." He was right; three days later, we were on a plane to go to the Seattle Boat Show... where we were able to see, get a ride on one, and buy.
Ranger has been in business for a long time, but I don't think that translates to the kind of numbers that C-Dory has produced over the years. I would guess there are just not a lot of Ranger Tug 21 owners here on this site. (After all, it IS a C-Dory owners group, and only with the premise of the C-Ranger 25 Tug joint venture about 2 years ago did the tug folks show up here). Don't get me wrong - I enjoy the perspective of the tug folks here; admire their boats. But, if a Ranger tug owner has had their boat more than two years, they likely don't even know this site exists. I did a Google search with "Ranger Tug 21" and came up with 123,000 possibles. Sure, a lot of those are going to be fruitless, but you MAY find more info. In all probablility, you will find that the results of other owners WILL be about the same as the two responses you got here.
This is just my two pesos opinion (yours free, today only), and is not meant to be pointed. You have asked questions, you have gotten answers. The boat just doesn't do what you want it to do. You can ask more people, but the answers really aren't going to change. That neat little boat was designed for a purpose, but going fast isn't that purpose. Unlike the go-fast boats that you have run, you can't just shove in more horse power and expect to see similar results - it's a relatively short waterline and a hull not made for planing - that's not bad, it's just what it IS. You could hang more motors on the back, make the boat goofy-looking (in my singular opinion), make more noise with it, burn more fuel (and two different types of fuel), complicate the whole boating experience, and it just isn't going to go a LOT faster.
We all get it: you like the looks of this boat. And if that's reason enough for you to want to buy it, that's the only reason you need. There are plenty of people who own more than one boat - different boats for different missions. The solution to your dilemma is pretty easy - TWO BOATS... the Ranger Tug for the looks and efficiency, and a go-fast boat that will run the speed you want, when you want, without a lot of inefficient modifications.
You don't buy a race horse to use as a pack mule... and you can't expect a pack mule to ever win the Kentucky Derby. That doesn't make either animal a bad choice - as long as
you make the right choice for the mission.
The owners who participate here have generously shared their experiences with you. If they don't want their boats to go faster, accept that they have a different mission for their boats than you. If the boat doesn't go as fast as you want, asking more people won't make it go faster.
There is yet another option - go to a marine architect and have them design and build a boat that looks similar, but with a different hull design that will go faster. You CAN have exactly what you want, if your budget and patience can handle it. Don't expect an MA to cut you a deal with the idea that he can sell the plans to others... this truly sounds like the answer to a question that no one else has asked. (Much like the general reaction to the C-Dory 29 :crook )
I was told what to expect the weight of my boat to be... the manufacturer missed it by almost a TON. I knew what to
really expect when other owners shared their experiences with me. I tend NOT to believe advertising HYPE until I have seen real world verification. Forget what you've read about the speed of the 21 - unless it's from other owners. Even if boat magazines had run their own tests (and I've never seen an issue of "Fast Small Tugs Monthly"), that would be on a lightly loaded, partially fueled, perfect water conditions, no adverse wind situation... good luck EVER duplicating that.
Sometimes you can get exactly what you want in this world. Sometimes you have to make compromises. Sometimes you need to accept that some things are just NOT going to happen, no matter how much you'd like them to. (Hey, I'd like to win the lottery, but that's NOT going to happen, because I don't buy tickets

) Feel free to consider this post a smack upside the head... you coulda bought a V-8. :wink:
Dreams and goals are important, as is being realistic. It's not realistic to think that a production manufacturer will want to make a one-off boat. It's not realistic to believe that lots of other people want what you want - especially when there's been no evidence of that here. It's not realistic to believe that reasonable horsepower will overcome a hull design. It's not realistic to believe that fuel prices will come down enough to make a higher fuel burn a more desirable trait in any design.
No intent to burst your bubble, just hope to expand your options with some real world observations. And that's the end of my free opinions on this subject.
Good luck with your search.
Best wishes,
Jim B. (with a little too much time on my hands this morning)
PS - You may come up with a design that will make you a small fortune in the boat biz... you do know how to make a small fortune in the boat biz, don't you? Yeah, start with a big fortune.