C145 allowable rpm limits

[flyguy]

In our (Deana and OLE GAR) fleet of 4 airplanes, there are three with Conies turning the windmills. I have owned '93D over 30 years and am on the fourth engine. Like friend BlueElder, I have turned the tar out of the C-145 and O-300 engines. Except for the prop strike on #2 engine I have run all of then to or beyond TBO with no more wear and tear on anything but the cylinders. I feel the 2700 RPM limitation is generous because the GO-300 I have on the '61 C175 turns 3150 to develop the 175HP advertised. The cylinders are modified for higher compression. The recomended TBO is 1200 hours(!) BUT I am well into 1500 hours and compression is still good. I am just forging ahead because I intend to up-grade the mill when it goes south. I want to re-engine it with a de-rated 210 Continental off a 172XP.

Best Cruise Speed in an airplane is most efficient. When you cover the most ground with the least time (and less stress) spent on the engine you are getting the most bang for your buck. I have the "Cal-Twist" prop on '93D and at 2650 at 7500msl I usually indicate 135mph. Fuel burn is usually around 9.5 but I have consistently gotten 14 to 15 mpg at that rpm. Turn slower - go slower, and get 14 mpg but put more clock hours on the engine and your butt. TBO will not change too much either! The quieter ride is one benefit of 2400rpm cruise. That is about it though.

Lets go FAST!

[Collin Gyenes]

Hi,

Lots of good reading on props.

I put a Cal-Twist prop on my 170B three years ago. I have been happy with the climb performance. The cruse is a little better than my old 76/53.

[AR Dave]

I know it's hard to state, but how much better does it climb?