That seems like a lot of power loss compared to a standard Bravo. Anytime you have to turn more mass or a mass is harder to move by design, it'll take more power. That's why the B-Max will slow a boat down, but you gain the strength that the bigger gears provide. In F3, the boats that ran a No.6 would be slower then the same boat with a Bravo, but the 6 gave them the reliability the Bravos lacked in the rougher water when the boats were prone to flying.
Craig