I'm currently building the Dumas "Miss Unlimited" 1/8 scale kit. It was originally released in the 1960's as a glow powered, tethered set-up. I'm using brushless electric and lithium batteries. The running gear I'm using is essentially the stuff that comes with the Pro Boat U-19 30" long ready to run hydro from Horizon Hobbies.
https://www.horizonhobby.com/product/boats/pro-boat-brand/electric-boats/ul-19-30-inch-hydroplane-rtr-prb08028
I'm building for fun, not to race. I'm setting it up to run counter clockwise, like the real boats, where most model racing is clockwise as a function of the direction the motor turns. Besides, this kit is too heavy and is otherwise not a competitive design. The guys who are "seriously" racing their toy boats have much more advanced designs, and virtually every boat is fiberglass and carbon fiber.
There is a very active local club, known as Classic Thunder, who race on a number of lakes in the Puget Sound area. I went and watched a few of their races in Marysville last year. They run several classes, from "vintage" to right up to date.
Classic Thunder 1/10th Scale Electric Hydroplane Racing
These guys are probably far more serious than you want to get about all of this, but it still pays to go to their races and see what they do. They always have boats for sale, too, if you want to jump right in. Me, I wanted to build something.
The Dumas kit is everything you have heard it is. It sucks. Poor quality wood, imprecise die cutting of that wood, bad instructions, and on and on. It is a challenge, definitely, but only because it is such a bad kit. But, to be fair, it is a product of the '60's, and has not been updated. I've grown used to modern CAD designed kits with laser cut wood where everything fits. I'm spoiled. This is not that, not by a long shot. I suppose just using their parts as templates and cutting parts from better wood might help, but not much. There is still an awful lot of hand fitting and room for "interpretation" in making it all "fit", more or less.