I ran a hyromotive 26 pitch four blade until yesterday on my baja 272, my boat will porpose in calm water under 3/4 to full throttle runs when all trimmed out. I know a hook in the hull will cause this and had mine check and the wasn't one. I was told that my boat will tend to do this in calm water because of its length. It is almost like it is looking for the next wave to run through. When I get her out in to some chop it runs faster and no porpoise because there is less friction on the hull. I got a bravo one 4 blade 28 pitch and ran it yesterday and it performed better and I did notice a little less porpoising than the hydromotive.