The guy that I bought this from did the rebuild to the lower unit, He had a 23p prop on it before the rebuild but after they were done he said the 23p prop wouldn't fit and the only prop he had around that fit was the 27p prop. After that he said when he'd get enough weight on the boat (2 grown adults plus gear) it would ventilate which caused the rpm's to jump way up and slip on the water. He demonstrated it with the 2 of us in the boat. It had problems getting on a plane if he just punched it, like the prop wouldn't grab, it would slip, the rpm's would go way up until he backed off the throttle and slowly got on a plane. Once on a plane it was fine cruising at about 57mph but I could feel the boat at different trim heights would slip some, it just wouldn't bite water correctly if that makes sense. I've had the boat out probably 15 times since August, its not a spun hub, I've had plenty of those...and by myself the boat just jumps out of the hole like it was nothing. But cruising by myself at different trim heights I can feel the prop isn't pushing the boat correctly. It's slipping just going straight until I move the trim some. The only reason I went to a 19p prop is because I used Turning Points Prop Wizard. In the wizard you enter in all your boat, your motors, gear, accessories into this wizard and it tells you what prop size you should be running. So I just went off of that. With the 27p prop I was only getting to 4500 rpms by myself WOT. Now I read that 1 inch of pitch equals approximately 200 rpms so in theory I should have gone down about 3-4 inches in pitch. So a 23 pitch prop should be about right but I trusted Turning Points prop wizard more than what I read. According to Evinrude my motors WOT should be aprox 5200 rpms for this model. I figured it would be to much rpms with the 19 inch but I figured I just wouldn't go WOT and just go to 5200 rpms.