The International Cessna^® 170 Association

What advatages are there in using either a 1IA170 DM7651 McCaulley prop VS 1A175-DM 8043 McCaulley prop?

One is 76 inches dia. and a pitch of 51 inch pitch. (ideally)
The other is 80 inches dia. and only 43 inch pitch.

Does the additional 4 inches make that much difference that you would notice it?

I am flying behind a 1IA170 DM7651 now.

Speaking in simple terms.

With the 80/43 the reason the prop has to be longer is so you don't/can't over speed the engine with the lower pitch of 43 verses 51. So again in simple terms the 43 pitch is a flatter prop and there for you will get better climb or at least to an efficient climb speed faster. There is a point of diminishing returns. A 38 pitch might not have enough bite to move the plane to a desired climb speed effectively within the limits of the engine RPM and climb would suffer.

There is of course a lot more to it. Blade size, airfoil, overall prop efficiency all come into play.

If you want maximum climb out of a 145 conty, go 8043. I fly mine out of a 650' strip with trees at the end...If I ever figure out how to post a link to a video, I'll show you.

Joe

I use an 80/40. can't go very fast....Floats,wheels, skis

I have a 80/42. It makes a huge difference in takeoff roll and climb, especially if you are light. Its preferred equipment here in AK for guys who fly with the stock engine, regularly land off field and/or operate out of short strips, and fly heavy. It may be the best STOL mod you can find.

There is a significant trade off however. Once you are airborne, they are slow..kind of like driving around town in 1st gear all the time. At 2,450 at 2,500msl, I am lucky to get 95 mph. (8x50s and other items don't help either.)

If I were generally flying off paved strips greater than 2,000ft, I wouldn't even bother with it unless perhaps I were flying out of higher elevation strips. Although our local strips are short, our density altitudes are usually very low so w at least have that going for us.

Yeh but it'd be harder to give it up than you think Pete. Six years down here and I just can't give up the climb performance. I've decided that I'll just live with the 100 mph max and keep my 8043. Don't think we could've done that Colorado Trip with out it, I'm serious.

I installed the 1A175/DM 8042 this spring and it was well worth the price. I operate on floats most of the time and the performance off the water is very much improved. Climb is impressive and the 145 doesn't seem to be as burdened as it was with the original floatplane prop. In my opinion the 8042 should have been the originally approved floatplane prop. It seems ideally mated to the engine. Both on the slide and climb, the 145 is turning a lot faster and developing significantly more HP. It gets up on the step quickly and climbs effortlessly at 80 MPH. I don't have to worry about getting off the water at gross any more. I haven't operated on wheels yet but am sure it will lift off and climb even better. The speed penalty isn't more than a few knots. I'd much rather get off the water than get there in a hurry.

I have the 80/43 prop. I put on for back country flying. I took off from Big Creek Idaho with 3/4 fuel. 300 Lbs under gross (All the camping equipment I needed for four days and my mountain bike) was off by mid field and climbing at 800 ft/ minute at about 70 degrees outside air temp. This is not very scientific but I would not want to be doing that with the stock cruise prop I have for other uses. Big creek 5,743 ft MSL 3,500 ft long

Jim