You guys running the 4 stroke outboards, have you replaced the prop or you still using the one that came with it ?
You should be using one with less pitch 7" , the one supplied is 8" , makes a big differance , lets you get up to RPM faster and less slip . 8" pitch is for planing dinghies and jon boats , some mechanics even suggest 6" or 6.5" pitch .
A prop shop can re-pitch it for you for a few bucks ( cheaper than a new prop ).

Mike G