Which engine do you have?
By the way, my LCA is NC37818, s/n 329, one serial number after yours. Wasn't yours in a museum in Fond du Lac WI a few years back?
I'll assume you have the Franklin 4AC-199E3. Based on that, the numbers you are showing seem rather odd to me. The standard propeller for the Culver L-AR-90 (essentially a Cadet with tricycle gear and a 4AC-199E3) was a Sensenich 70AF56, so that should be the right propeller for you. You may still be interested in an adjustable pitch propeller, but I don't think the fixed pitch prop is responsible for these odd numbers (unless possibly you are using a different model than the AF). With a 56 inch pitch (fixed) prop, I would expect approximately 2300 static RPM and approximately 2500 to 2550 RPM in level flight with full throttle (with a true airspeed of about 115 knots @ 2500 RPM), with the climb RPM somewhere in between.
The very low static RPM and very high full throttle level flight RPM are what I find particularly odd. Have you verified the RPM with an optical/digital tach? Mechanical tachs are often inaccurate. Your airspeed indicator could also be inaccurate. I've found a few old Aeromarine airspeed indicators that read about 10% higher than they should. Beyond that, I would investigate the engine (things such as ignition timing, throttle operation, carburetor adjustments, etc.) as a cause prior to changing props.
Unfortunately I don't know of any good solutions for an adjustable pitch propeller. Culver originally used Freedman-Burnham ground adjustable propellers on the Cadets, but changed to fixed pitch Sensenich props sometime fairly early in production. Here's a link to some photos of Freedman-Burnham propellers including one on a Culver:
http://www.notplanejane.com/freedman.htm. I believe an airworthy Freedman-Burnham will be fairly difficult to come by. They've been out of production for a long time. I don't know of any certified adjustable pitch propellers currently in production. Sensenich makes them for experimental & LSA.
