I'm new to Super Cubs. Love it.
I hope you'll forgive me if this question was asked before, but I can't seem to find an answer buried in the forums.
I have a PA-18-150. (does not have the 160 HP mod) Has the Sensenich 74DM6-0-56 prop with fewer than 50 hours and in good condition. Compression is within mid 60's to mid 70's.
Before and after the recent annual, I am unable to produce RPM over 2500 in level cruise (2475 ish). Static RPM is about 2250.
We checked the RPM at a few settings with a hand held device. The tach is very close to indicated, although the needle does swing occasionally at high RPM settings. It always settles.
After flying a square on cardinal headings, I'm getting about 100 mph according to calculations. Airspeed indicator seems to be off as well. Pitot has a very slow leak.
My mechanic says he doesn't think I'm developing full power. Another mechanic says its about right for the age of the engine (3000 + TT, 275 SMOH) and standard prop. They will be taking a closer look soon. Yet another mechanic thinks I should get more RPMs.
While I sort it out, I got recommendations to use Marvel Mystery Oil in fuel, check valve clearance, check for intake manifold leaks, check carb butterfly for full opening. The throttle and mixture cables have stop-to-stop travel.
I understand all planes are different but I wonder what max RPM are other PA-18-150 with standard props are getting (Are there any PA-18-150's with standard props anymore? I plan to order a Borer 8242)?
I know this topic has been discussed here before. I appreciate helping a newbee.