Choosing a prop to solve a problem

I have a 1999 aluminium Starcraft 19 1/2 ft Fishmaster powered by a 150 hp Optimax engine. This boat has a 50 gal gas tank that seems to be located in the center to stern of the boat. It also has a 9.9 kicker mounted on the stern. My point being the the boat is stern heavy. The prop is a Laser II 3 blade
14 1/2 X 19 SS. There are two problems I would like to correct. It is slow to plane and when cutting back the throttle the stern settles back into the water. It has been suggested that by changing to a 4 blade 14 1/2 X 18 or 17 the problem should be corrected. Any opinions or suggestions would be greatly appreciated.

Also, if I do this should I buy stainless or aluminium?

Thanks
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