I have a SD 2400 with the Yamaha 250 OB. I'm having trouble figuring out the trim. At any speed and any RPM, my RPMs increase when I trim the motor up any amount. Therefore, it appears that in just about all conditions and speeds, my best trim option is all the way down. Can this be right, or should I be looking at something other than RPMs decreasing a little to determine proper trim plane.