The Cessna 120-140 Association Forum

Hi Folks,

I have a C90 with CM7152 on it. There is a CM7147 for sale nearby and I'm considering buying it to have two props, one for cruising and one for playing in the backcountry. My Static RPM with the 7152 is ~2050 and I have checked it with an optical tach. I have concluded that elevation I do the test at doesn't matter as the decrease in engine power is close to proportional to the decrease in drag on the propeller.

Does anyone have experience swapping to a climb prop they would like to share? What static did you start with and end with? What pitch to what pitch?

Marshall

Flew from Chicago to Tucson was afraid our C-90 wouldn't have enough to clear the mountains so removed our 71-50 and borrowed a 71-46 lost a good 8mph but performance was great did have to keep a close watch on the tach. that prop was easy to pass redline. Can no recall all our static numbers but I assure you it will make a huge difference from your 52. Good Luck

7150 is considered a climb prop for the C90 on a 140. At 46 pitch I'm surprised you use full throttle on your takeoff run without exceeding redline!

Hmm, interesting. Ideally I was looking for a 48 or 50. But a 47 is awfully close to what I am looking for. I don't have any clue what difference 1,2 or 5 inches will make to my RPM or takeoff performance. Like I said I'm on the low end of my Static RPM so I have some room to move, just how much is what I'm trying to figure out.

Anyway thanks for the input.

Can you borrow it?

Don't forget, you need to meet the static limits in the Aircraft Specifications. A 46" may not. For the McCauley, not over 2350, not under 2050.