Yes it would use WAY more gas. 5000 RPM's is way to high for your engine. It was not designed to run at red line rpms all the time.
Did some one recommend that prop?
Not only will that prop empty your wallet it will shorten the life of your engine
I would talk to Eric at OJ props email@example.com
or Bill Weeks at Acme firstname.lastname@example.org
they can recommend the right prop.