I have a '99 Chaparral Sig 27 w/7.4 liter MCM 315 hp and Bravo 3 drive. With fuel, water and stuff, the boat must weigh 7000# plus. I currently run 24" pitch uncupped props. The engine says WOT should be 4200-4600 rpms. Trimming out the drive and a moderate load, I run 39 mph but only 4100 rpms. <br /><br />With the counter rotating props, how is the RPM calculation different? Hole shot is okay (I've always had a much smaller boat), but using the trim tabs definitely helps. I've thought about 22" pitch uncupped or 20" pitch cupped props, but am still not sure. I know the Mercury cupping on these B3 props are not very aggressive. Just the trailing edge is cupped, not the entire blade surface.<br /> <br />At $1000 a set, trial and error is really not a viable option unless I get myself a good divirce attorney after I buy them. 
I'm looking to help with those days of heavy loads, wind and getting up on a plane with the canvas up. <br /><br />I've checked the calculators, but still need more clarification. Every prop shop says something different. Anyone else have some words of wisdom or a boat similiar in size and power/drive?<br /><br />"I am my own worst enemy"-Fishnfreak
I'm looking to help with those days of heavy loads, wind and getting up on a plane with the canvas up. <br /><br />I've checked the calculators, but still need more clarification. Every prop shop says something different. Anyone else have some words of wisdom or a boat similiar in size and power/drive?<br /><br />"I am my own worst enemy"-Fishnfreak
