5800 RPM's is the about the maximum revolutions you should be turning on a Merc 225 EFI. The Pro-Max will go much higher on RPM's, but these engines are designed for about 100-150 hours before they explode like a Palisenian Suicide Bomber. Props are like tires on vehicles, they all ride differently. The Gambler is notorious for a slower hole shot than most hulls due to all of the weight being in the rear-end (my ex-wife had the same problem). The top-end speed makes up for the slow start. The three blade will take a little longer to get up than a four blade prop, but it will push the boat faster than a four blade at the same RPM's due to the amount of water the blades will catch at higher speeds. The 4-blade Merc Trophy is a good prop and a 24/25 Pitch would probably do you right. Make sure you load the weight to the boat before selecting the final prop, fill the livewells, get your mother-in law in the boat and all your gear to make sure you are load testing the Gambler correctly. That should get you where you want to be. Good luck and wear your PFD and kill switch when the big engine is running.