I have an M5-235 (Lycoming O-540) on EDO 2440 floats with a Hartzell HC-C2YR-1BF/F8468A-6R propeller. I don't know much about props or model numbers but I assume that this is an 84" prop. It pulls the plane out of the water nicely and cruises at approx 120 MPH at 60% power.

I'm pondering what a larger prop would do for me and am looking for pro's and cons. If I recall correctly, a larger prop will get me out of the water quicker and improve climb performance but slow my cruise speed. Is this correct?

If this is an 84" prop, and the above theory is correct - will an 88" make a big difference? 90"?

Also, what does a larger prop do to engine wear and tear as well as fuel consumption?

What is 90" prop worth?

I'm not planning on having the plane on wheels.

Sorry for all the questions.

garth

If you put more metal out front you will take off sooner and climb better but cruise slower. Here's a table from the folks at Pponk that will tell you what happens with different size props.

http://www.pponk.com/HTML%20PAGES/propellers.html

Hello gear
The 84 is the base design prop diameter.The -6 number should mean it is 6 inch shorter blades.Measure the prop tip to tip to get the current diameter.
For a given blade design a longer prop will produce more thrust but there is more to prop choice than that.
Prop choice for a certified aircraft will be limited to what is called out in the Type Certificate or what has been approved by STC.A call to Maule or the prop manufacturers will get the approved prop info.Some props seem to work better than others in certain applications.
Also on the constant speed prop the pitch stops are sometimes set to allow a flatter pitch when used on the floatplane.If your prop was set up for a wheel plane it may need to be adjusted for optimum float performance.
Most of the seaplane props I have seen are a little more expensive than the landplane.It depends on the application.
On my cub with 0-200 I use a Cessna 150 seaplane prop.It is a MacCauley 75 inch diameter/35 pitch.The 150 landplane prop is a 69/44.The seaplane prop gives way better take-off and climb.The flatter pitch lets the engine come up about 100 rpm more and the long blade provides additional thrust.
As far as wear and tear I don't think it is a factor.It really should not slow the plane down in cruise if the pitch is optimized for the plane and load.
I actually cruise faster and get better fuel consumption numbers than friends with landplane props.

Bill

What BIll said, with one additional caveat: The first step in getting any prop approved on any engine is to complete a full vibration survey of the prop/engine combination. Once that's done, then the prop has to be approved on the aircraft, as Bill said, either via the TC or STC.

Your prop is a 78 inch diameter, based on the designation. The -6 means that six inches have been cut off the base blades. The prop manufacturers do this so that they can use the same base blades on a number of different engine/airframe combinations.

Another consideration on prop length is prop clearance. On seaplanes, water is VERY erosive, and if you have a very long prop, you may wind up having to dress the ends of the blades frequently to remove the pitting. Every time you do that, you'll remove some more of that precious metal.

I don't know what props are available for the Maules, but I'd check MT propeller to see if they have any props approved for that airplane. Those props do REALLY well on seaplanes, with a stainless steel leading edge strip, which virtually eliminates water erosion.

And, the MT props perform well, as well as being quite a bit lighter than a metal prop.

Finally, I flew a Maule M-235 on floats for a few hundred hours, and in the process, they changed the two bladed prop for a three bladed prop. I really didn't like the three blade, due to the weight of it, which made for a more forward CG. Eventually, they went back to the two blade. So, consider weight as well as length. Call up the MT guys--Larry at 612 619 5782, and see what they can do for you.

OH, yeah, props are not cheap.

MTV

Thanks to all three of you for your responses. I learn something everytime I go on this site. I'll do some digging / reserch on this and see what I come up with. I'll also talk to my AME on the pitch set up.

During my rating , I flew a C-172 and a 180 with 90" prop's on them. They got me out of the water pretty quick. My M5 has the same HP as the c-180 but the 180 sure seemed to have a lot more power, considering the weight is higher as well. I'm thinking this was all due to the prop. I did get the low down from them on the increase in water errosion so I know that is a drawback.

I will have the plane loaded quite often so I'm thinking I could really use something longer. Will investigate further.

Is there a market out there for prop trade ins? mine is in mint shape - very low hours on it.

Garth

Hi Garth,

Looks like summer finally made it to our part of the world. I have a new (longer) prop on the 185 this season. Have not flown it enough yet to decide how much better it gets off the water, but it sure makes a lot more noise. How about trying Barnstormers to get rid of your prop? Steve

Steve brings up an important point - that being noise. If you are coming and going from a place with neighbors that aren't as crazy about planes as you, the long prop can get some complaints. Nothing like a 185 turning a 88 inch prop at 2850 to wake up the neighborhood. Also, some of the 3 blades develop better thrust on some engines and can have a lot less vibration, which in the long run means less wear and tear on your airframe. Pponks website has interesting data, and in their tests the 3 blade 86 MAC outpulled everything on the big Continentals. It actually pulled the same as the 88 inch 3 blade, and their theory was the 88 inch started wasting energy making noise. Anyways, there is a lot of black magic with props and I can't say I understand it all. If I were you I'd get on the Maule website and see what guys are running on 540's on floats over there. One of the Maule boys in Georgia could probably help you too. Russ

I went to the Mac 401 86 inch 3 blade from a shorter 3 blade. Interesting how it noticably pulls better when you back off the RPM's after clearing the water. More so than the old prop.

Steve, have you tried that lower RPM setting during the takeoff run ? I wonder why it would pull better wide open on the water but not in the air? If you don't mind me asking, what did your prop cost? Did your cruise speed slow down with the bigger prop? Enough questions. I have an 82 3 blade MAC and it does fine on my Pponk motor on floats, but if there were a lot to be gained without too much money being lost, the 86 inch MAC could be in my future. Russ

I was going to put something on the maule pilots site regarding what other people are running so we'll see what they say.

Noise is a slight concern, but I think if I'm looking for decent float takeoff performance - I need something longer that 78" -when the plane is loaded - it just doesn't quite have the performance I'm looking for.

I did start looking on Barnstormers so maybe I can look into a trade.

Russ - hope your 185 is treating you well!

Actually a 182 with the Pponk motor upgrade and Aerocets, and it is a dandy float plane. My friend with a M-7 and the 540 on 2440's is running an 82 inch 3 blade on his (Mac I think). His performs well, but as I recall the M-7 has more wing than the M-5. He also had his wing modified to give it more aileron - the M-7's came with ping pong paddles for ailerons originally. The wing on the M-5 could be as much a limiting factor for gross weight float takeoffs as the prop. I have the wing extensions on my 182 and it sure seems to lift off and land slow, but I never had it on floats without the extensions so have nothing to compare to.

Russ,

I have been backing off the RPM on the takeoff a little anyway, as I have an endless supply of lake length and want to keep the noise down. Not sure about about airspeed-cruise loss, but for my application PKD is probably about as far as I'll ever go in it anyway, so for once, speed is no big deal. More concerned about payload. Got the prop from PPonk and paid $8524, tried to look up installation cost from Park Rapids, but could not separate it from some other work done. You are welcome to try it out, when you are on this side of the border.Give me a buzz and I can fly over. I need to harrass Roger Peterson anyway. Steve

I think the only 3 blade STC for a M5-235C O-540J1A5D is an 80" McCauley.

I think you can swing an 81" or maybe an 82" w/ 850 tires on a M5.

I had a two blade Hartzell on my M5 and swapped to the 3 Blade McCauley and never looked back. Faster on the step and far quieter both on the water and in the air.

I would run this question past Jeremy Ainsworth over at www.maulepilots.org

Tom