New to me Parker 2120 - mercury v6 prop help!

[Jrpalmer]

Hi, just acquired a 2003 Parker 2120 that had an older HPDI on it. I came across a display model Mercury 200hp v6 and could t resist it. The problem is, I can’t find any other Parker’s out there with this set up and I’m not sure what prop to run. The shop that did the instal was 0 help, and since I had no prop to even test it I went to Mercury’s website and used their propeller selector tool. The recommended prop was a 16x16, which seemed odd. I did put that on but I can only get about 5100 RPM’s out of it loaded. I would like to buy a better prop for it but I don’t really just want to keep buying props until I find the right one. Anyone know what prop would be good for all around fuel economy? I’m usually running pretty heavy. Thanks!