Hmmmm.......
Never really looked that close at the Utopia, always deemed it ugly and expensive.
I beleive all the Utopia's had the mercury 240hp jet which was basically the top of a merc 225 o/b tweaked to 240hp mounted inboard and had a jet drive stuck up it's arse.
The single merc setup fares better than the old twin rotax with much better fuel economy, better reliability (although merc parts are ultimately much more expensive than rotax, and obviously, if you do have a problem out at sea with the merc, you don't have the advantage of a spare engine to get you home)
http://www.jetboating.net and
http://speedster.gapmanwebdesign.com are both quite useful references.