The props are installed by the factory before they ship to a dealer. On the newer Z17 models with a 115 CT, the factory recommends (and comes with) a 22p Tempest Plus with the engine mounted in the fourth hole. The factory also recommends running three solid plugs in the prop for best hole shot. What year is your boat? I can see if I can get more exact specs for your Z6. The last two years Nitro built the Z6 models (2015-16) they offered a 115 CT and ran a 25p Fury (sounds crazy, I know) on them. The engine was mounted 3" above the transom (probably around the 5th hole). I hope this helps.