The power boat is at fault. first of all, the collision itself is prima facie proof that he failed to "keep a proper lookout"

Second, the "General Prudential Rule" in COLFREGS definitely applies in this situation

ColReg 2(b) — "In construing and complying with these rules, due regard shall be had to all dangers of navigation and collision, and to any special circumstances, including the limitations of the vessels involved, which may make a departure from the above rules necessary to avoid immediate danger.”