Time to change props. I've got a Crownie 225 BR with a 5.7 Volvo GSI and an SX stern with a 1.43 gear ratio. The PowerTech 18p 4 blade SS works great at 1000 ft. However, I'm up at elevation and barely getting 4000 rpm out of a 5000 max RPM motor. I'll be going with another 4 blade SS...