Propeller Specifications

Robert Eilers · Post by **Robert Eilers** » Fri May 04, 2007 9:59 pm

I am interested in improving the takeoff and climb performanace of my 170B; which is currently equipped with a McCauley 7653 - 2330 RPM on T.O. I explorered the California or Jet Flow propeller modification. I am coming to the conclusion I might be able to provide myself with improved performance, without going the Aero Propeller way, by having my local prop shop modify the existing prop. However, I am not certain I understand the prop specifications, i.e., 7653, 7655, 7651, etc. I am looking for something between cruise and climb that will give 2500 - 2700 RPM on T.O. I had great success doing this with the prop on my Champ. Is there some document I can refer to better identify the performance characteristics of the different specifications?

Post by **GAHorn** » Fri May 04, 2007 11:50 pm

The number "7653" refers to a prop which originally had a diameter of 76 inches and a pitch of 53 inches. If you decrease the pitch to 51 inches (to obtain greater rpm at static/takeoff, then the prop would be re-stamped "7651".
If you have the pitch of your prop reduced so that 2700 rpm is attained on takeoff...you may find your engine turning excess rpm at cruise and you may have to reduce cruise power significantly to prevent engine overspeeding. This might not be the result you wish for.

4stripes · Post by **4stripes** » Sat May 05, 2007 10:24 am

My 7651 prop (51" pitch) is a good compromise. T/O and climb performance is good and cruise of 100Kts is decent too. I used to fly into many mountain and island up-prepared airstrips when based on the west coast. Now that I'm in flat country a 53" pitch may get me another 4 to 5 knots, but I wouldn't bother changing it.

Cheers Eric

bodine · Post by **bodine** » Mon May 07, 2007 7:31 pm

Hi I have a 52 pitch prop on mine and see about 107 with decent climb perf. But it came on the plane when i bought it and have never flown any other 170....