"Trimax is a drive system with a surface piercing propeller completely locked in the running position. However, it is possible to set it in the space of a few minutes to obtain the best possible speed. The fixed shaft with the rudder at the rear of the propeller ensures directional stability at any speed. A trimable drive is also available for special applications.

Its simplicity and consequent reliability make Trimax the surface drive with the least mechanical friction and the smallest degree of propeller shaft inclination (3° to 4°) and therefore there is no doubt that this system offers optimum performance.

Proof of this lies in a string of wins in offshore racing; with more than 30 world championships in all existing offshore classes Trimax is by far the most winning."

See:
http://www.fbdesign.it/