Charlie, If I remember correctly, for the 75 it should be a 73" dia. with 71" perhaps being the minimum for repair. The pitch is finer than that of the 85 prop, so it should be 7351 (I think) for the 75. If you install a 85 HP prop on the 75, you "may" get the same performance as the 85. 85 props are 7150 std, and 7148 climb, with 69.5" being the min. for repair. The shorter prop allows for the acheivement of the higher rpm of the 85. The 75 hp McCauley specs are in the Service Bulletins and Memos. The spec for the 85 hp McCauley prop are in the Univair catalog.
Speeds. We used to fly 3 Ercoupes in loose formation with a Cessna 140 with 85 hp. The other two Ercoupes airspeed indicators read higher than mine. They said, "they cruised at 110." My coupe, indicated 100 (110 WIDE OPEN LEVEL !) was faster than theirs regardless of the indicated airspeed. And, alas, the Cessna with the same prop and engine could steadily pull away from me when I was wide open. My prop is a 7150 which now measures at minimum diameter of 69.5". I have had people tell me their coupe cruises 110 and even 120 but it ain't so. In the real world, and if their airspeed indicators were right, more like 100, 105, 109, depending on model, engine, etc. Engine condition. Prop. Rigging. Drag (mucho antennas, etc.) Getting on the step. All of the above, and more, impact top speed and cruise speed at a given rpm. Oh, and the top of the canopy is a real source of drag. Do you fly with yours cracked? I have put a shade panel in mine and the two side windows which used to meet at the top not just come up to the edges of the shade window which is Smooth on top. Really, a 75 ought to go just as fast as an 85 hp model, assuming both have engines that are not "tired." Grover 99398 Columbus, GA On Thu, 25 Feb 1999 10:00:39 -0500 "Charlie Nightingale" <[EMAIL PROTECTED]> writes: >Need to know if anyone has the following: > 1. What is the correct Mccaully prop for a 75hp Ercoupe under >cruise >conditions.The numbers on mine have been overmarked and >are not readily readable. It looks like CM 71.??. My speed is only >about 98 >mph by GPS AT 2450. I believe it is a CLIMB prop?? >Charlie N555CN Farmville,VA. > > ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]
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