I got my PA-22/20-150 home from Kansas the other day. It has Sullivan tips, VGs and 8.50 tires and I was interested what the cruise speeds would be.

True airspeeds at 3500' were:
2400 rpm 116 mph;
2450 rpm 120 mph;
2500 rpm 125 mph;
Fuel flows were about 6.5, 7.0 and 7.5 gph respectively, block to block, take off to landing with 2.5 to 3 hour legs.

It had been presented as having a stock 61" propeller pitch, but the fuel flows suggested it was operating at a lower pitch and correspondingly lower manifold pressure.

Looking at the stock O-320 power chart in a Tri-Pacer manual and the fuel flows listed, it appeared to be producing similar numbers with about 200 more rpm than with a stock 74/61 propeller.

I never found any entry in the log to indicate when the propeller was changed or repitched, but I did eventually find the yellow tag for a reconditioned Sensenich M74DM-56 propeller. A little number crunching confirms the 56" pitch would be consistent with the 200 rpm difference noted above.

I wasn't real sure how I felt about it since I'd planned on a bit more cruise performance. However:

- Static RPM yesterday on a 65 degree day at 50' MSL and 30.03 in hg was 2400 rpm which is close to the 2400 rpm max on the type certificate and is probably optimum for rate of climb;
- O-320s are generally very happy cruising at 2400-2500 rpm and this one is very, very smooth in that range;
- 120 to 125 mph/104 to 108 kts TAS at 3500 ft isn't a bad cross country speed (in the same ballpark as a Cherokee 150/160, Warrior or C172);
- 7.0 to 7.5 gph gives a max range between 540 and 570 miles with a 30 minute reserve; while
- auto gas brings the fuel costs down to about $15 per hour at those fuel burns.