My previous Levi Triana from back in the early 90's with a pair a Steyrs was good for 40/45 knots and the Triana Tropica "Bullitt" with VP V8's on duoprops is quoted at 44 knots. "Viking" may have had the power, but way too much weight.
Certainly capable of 50+ but unless you go to 600hp and a form of surface drive; forget it.
I recently spent a lot of time looking for another one in order to acheive this level of performance, but blink and you have missed one. Quite rightly; they sell quickly but inevitably end up being re-powered well under power !
As the ex-owner of Viking I can tell you she was certainly capable of it. That’s not to say the double D4.2Ls weren’t a stupid idea mind you! We had 47 knots from her and were 400rpm over WOT so an increase in pitch would have taken her over the 50 knot mark easily. In the end we dropped to single engine and settled for 39 knots. Plenty!