I can't think of a more effective way of cooling the engine. I believe our two boats probably share the same outdrive system, black plastic that holds the prop shaft/rudder and turns the whole thing as one unit? There is a black plastic water pickup right behind the prop on mine.

Pull the hose off and blow through it, make sure you don't have something stuck in it. I think one of the things that keeps my engine quite cool is the fact that for some unknown reason, the water is dumped right into the muffler after it comes out of the head. And this isn't a special water cooled muffler... its listed as a helicopter muffler by tower hobbies if you want to replace it.

The only other way to pickup water is to have a pickup dipping into the water in front of the prop, right at the hull. Since its not in the prop wash, nothing is really forced in so you won't have much waterflow at low speeds... and probably about the same or slightly less at high speeds.