I own a hallett 240 with a 500 hp. the guys at hill props will help, I called them, told them what motor and boat I had. They told me about a prop, I tried it and it worked ok, sent it back to them, they re worked it, and I tried it again and its works great, Hope this helps, even if I am a little behind the post.
I called Bronson Hill and I think I will use them soon after I get the re-call work finished on my 496HO. With the correct push rods in the engine I am hoping to get more RPMs and top speed.