60 hp merc prop question.

I mistakenly posted this in general forum. Should have been here.
I have a 2005 Alumacraft Navigator with a 4 stroke 60 hp Merc. When I purchased new in 2005, the boat would not get up on plane for about 1/4 mile with 3 guys in the boat.
I took it to a local Merc dealer and they raised it two holes. It was in the second hole when I bought it (first hole being lowest setting). This brought it up on plane, but would cavitate while turning at higher speeds. By the way the prop on it is 13 degrees and a 10 and some odd inches across.
I just took it to another dealer, he lowered it back to original, and said it should have a 15 degree or maybe even 17 degree prop and maybe a larger diameter. (another $100.00) to get back to square one. The boat runs at about 5200 rpm with just me in the initial setting and 5500rpm in the previous raised position. The last position should return it to the 5200 rpm. Also the last dealer said alot of times the tachs are not accurate, and he wants me to run his portable tach on it first to see if mines off.
Everything that I have read leans toward the prop that I have on it is correct, or at least close.
Does anybody have this same setup (boat and motor) and have fine tuned it to the point where I won’t have to do all this trial and error? You wouldn’t think this day in age this would be all that difficult for expierienced boat people.
Thanks , Murf

If you couldn’t get on plane with a 13 degree a 15 degree isn’t going to either. It would make it worse.

Thats exactly what I was thinking on the way home with a lighter wallet…

Yeah and without much torque, The four strokes are known to be real dogs if you have too much pitch. I have a 50 yamaha and the props are the same way. I don’t have a working tach but it runs good with a 10-5/8×12 on a 500# boat.