The engine you are referring to is the Scorpion 350. Mercruiser has dropped the black designation for these engines and is referring to them as simply "Scorpion" for the 2009 tow sports market. The 350 is the indicator of the displacement, in this case 350 cubic inches. The horsepower rating on this engine with or with out catalyst is 330 hp. The Scorpion 377 produces 340 hp w/out and 380 hp with catalyst.
We have been exclusively installing the 350 Scorpion DTS with great results. Customers seem to really enjoy using the Launch Control feature. As for the performance of the Cat vs. Non-Cat engine I am unable to tell any difference in performance aside from the lack of exhaust smell the Cat. Engine produces. www.standardboats.com