Prop question - midrange yamaha 60hp

[mitserv]

Hey there everyone. I've been lurking for a while and decided to go ahead and post this. I was really hoping to get a few opinions about something that has bugged me since I bought my boat a couple months ago. I purchased a 2001 G3 Pro175 with a 1999 60hp Yamaha. The original alum prop was all banged up so I went ahead and purchased a replacement in (almost) the same size and pitch (13 1/2 X 15) but in a stainless. I installed the new prop before I ran the boat for the 1st time. The new prop is a Michigan Wheel Apollo model 13 3/4 X 15. I recently took the boat out for the first time and discovered my RPMs were easily able to hit 7000 if I were to push to WOT--obviously WAY too high. Recommended was 5000-6000. My cruising speed at the recommended 6000 RPM's was about 32mph and I was quite sure I had purchased the wrong prop. I checked online everywhere I could find (including here!) and cannot seem to find anyone who has ever had a similar boat/motor and asking about prop size. Now according to every prop size calculator I can find online, I should be running a 19p or 21p however the prop store I talked with said that this yamaha 60 would never turn that prop and I would never get on plane. My main concern is engine life but it would be nice to be able to get up around 40mph if it's possible in this boat. Okay, does anyone have any suggestions for me as I don't want to purchase ANOTHER prop that is the wrong size!
Thanks in advance to anyone who may be able to help.