A power trimaran is kind of an odd looking bird when you first look at one. Long skinny hull with very short amas. We have gotten used to seeing amas that are more than half as long as the main hull in sailing vessels. But of course the power tri needs a much smaller righting moment since there is no sail to rotate the boat around it's axis.They are much more stable that the equivalent monohull of course, and most of the recent long range power boat records have been set by trimarans of this type. An unrefueled crossing of the pacific was done several years ago with a pair of slightly modified 9.9 yamaha engines. and the UK navy has had a development program in place for some years and has begun to acquire a few. Here is a picture of one. Built in australia, I believe.

A beautiful Nigel Irens design - 21 meters, built way back in 1988
http://www.nigelirens.demon.co.uk/FRAMEpower.htm

And an Irens 35 meter went round the world in 1998.
http://www.nigelirens.demon.co.uk/nid_power2.htm