"Wayne" wrote in message ...
I am getting the 1961 175B Cessna that I mentioned before here. I am
trying to figure out how fast it should be. The owner said that it would go
GPH. Then I looked at the original specifications from Cessna. It
was supposed to cruise at 122 knots @ 75% power at 7500'. I had assumed that
he meant 125 MPH but that is only a little less than 109 knots.

Strange. I used to own a '59 Cessna and all of the performance
numbers from the factory were in mph back then. He probably meant 125
mph. The Skylark might be able to do 125 kts @ 75% @7,500' if the
plane is perfectly rigged and light, but the fuel burn he gave you
indicates that he's probably flying at 65% power. At 75% power
expect the O-360 to burn around 10.5 gph.

This has the
Lycoming O360 conversion with a constant speed prop, I would think that
would make it slightly faster and surely better on takeoff performance.

Why? The original Skylark made only 5 less horsepower and also had
a constant speed prop. Practically speaking I wouldn't expect 5 hp
to change the performance numbers a whole lot (particularly speed).

Real world, I'd expect to see 115-120 kts @ 75% @ 7,500' DA with
10gph for that plane, depending on its condition.

John Galban=====N4BQ (PA28-180)