I am trying to figure out what prop to try next. I have a 2001 searay 280 sundancer with 2 v6 4.3 liter engines, alpha 1 outdrives. The props on the boat now are 21 pitch but I dont know the dia. The engines will only run 3000 rpms and wot is suppose to be 4400 to 4800. Any advice on how to fix...