I have a 17' Sundowner with a 1989 20 hp merc 2 stroke. It has the original prop on it(10 x 13) and has some slip in her. Any recommendations? When she is dug in I am getting close to 30 mph with 2 people and gear. Should I stick with 3 blade or 4. I was thinking a Solas alum. would be a good fit. Thanks.