Boat Rescue. Prop Issues

Greetings BBC,
I took in a 1999 Ranger R71 that was needing a lot of help. I started with all new fiberglass lids and hardware from Ranger, new electrical, carpet, electronics, the list goes on. The motor is a 1999 Evinrude Ficht 115 that was well taken care of. All updates and was runs like a champ. Compression check didn't deviate 2 psi at 120 on all 4. I decided to go from 24 series batteries to Northstar 31 series, add a Minn Kota 15/3 and an Minn Kota alternator. 1st launch was a disaster. Had a new OMC aluminum 14 X 21 prop. I could not get this boat to plane out unless both my wife and I was on the bow and took 15 seconds. WOT was roughly 4700 rpm. I did the math and cheapo'ed a Solas Titan 13.25 X 17 ss prop. Second test run was much better, but still lacking. Planned out in 5-6 seconds WOT got me 44 mph and 5300 rpm. Great bite and handling, but this motor should be turning 5500-6000 rpm. So here is my deal. I can not believe that I need to turn a 15 pitch to get into my range. Motor runs like a top. Would a Raker 18 get me in there? I realize Solas may not be the best ss prop and are very stiff, but going to a 15 pitch seems crazy. Thanks for looking and tight lines!

Trane