I am using a 0s .40 and a evolution .46 and a os .91 any info on the prop sizes. This might be a dumb question but better safe than sorry. I have a wide range of props laying around, just want to know which ones will work on which motor. The smallest size to the largest size for each motor would be helpful. I would assume as long as it didn't hit the ground while mounted any prop would generally work. I currently use a 9/6 on the 40 a 11/7 on the 46 and a 14/6 on the .91

i use a 10x6 on a magnum 40
a 10x7 on a gms .47 or 11x5
and a 14x6 on a magnum 91 or 15x4

im a little confused at to why people run big props like a 11x7 on a .47 engine. what ever works for them i guess. or maybe its cause i run a low nitro (5%). but much above a 10x7 and it takes forever to spool up.


but for prop selection. pick what ever YOU want.
let someone get you in the prop range, like 10x7 for a .47 engine. then get a few different brands in a few different sizes and try then out.

ok maybe this will help here are my prop sizes in order of smallest to largest please point out which ones go on the 40 the 46 and the 91
1 wood zinger 11-5
1 nexstar prop 11-5 < assume this ones to the 46 since it come with the nexstar
1 wood top flite 11-6
1wood zinger 11-6
1 wood top flite 11-7
1 wood zinger 11-7
4 master airscrew 11-7
2 master airscrew 11-7.5
1 apc 11-11
1 rev-up pro series 12-6
1 nylon "super" 12-6
1 master airscrew 12-6
1 apc 12-7
1k series master airscrew 12-8
1 apc 12-13
1 wood top flite 12-8
1 k series master airscrew 13-6
and last but not least k series master airscrew 14-6
if I have prop sizes that do not work with these motors listed please point out which motor they work with thanks for any and all help

The GMS .47 produces a bit more power than other .46 engines, so you could go the way you did and use a 10x7 prop or an 11x6 prop for a heavier plane, but you can also use an 11x7 prop on a lighter plane to buy you both speed and thrust.

I've done it both ways and the larger prop works VERY well on a more lightly built .50 plane or a smaller .40 plane.

If it were me,I would go to wherever I could find the engine listed, like tower hobbies for instance and find the manufacturer recommended prop size for an engine and start there. Like your OS engines are here.. [link=http://www3.towerhobbies.com/cgi-bin/wti0002p?M=OSM]OS [/link] and the evolution can be found here [link=http://www.evolutionengines.com/]Evolution[/link] engines

You usually cant go wrong with the listed break in prop as a good starting point for any engine. In my opinion.

Here is what I found at tower about a .91 OS 2 stroke. Props: Hobby Services recommends a 13x8 or 13x9 prop (6/99)


COMMENTS: All FX series engines are covered by the O.S. two year warranty
Engine mounting & exhaust dimensions are the same as .61FX.
Engine guru Clarence Lee tached this engine w/various props
Prop Size RPM
13x6 12,500
13x8 10,400 using a 13x8 prop,
13x10 9,500 Hobby Services tached this
14x6 10,900 engine at 11,300 RPM
14x8 9,500 6-24-99
14x10 8,400
15x6 10,200
15x8 8,100
16x6 8,300

ok ill give it a go.
people at my field were like why are you running a 10x7 on that .47. you should use a 10x6
in the back of my mind im like "i have this old magnum that doesnt have much umph on a 10x6 why would i want a 10x6 on my nice and powerful gms .47?"
.....but they put a 10x6 apc on it.
i have a bunch of 10x7 MAS props that i normally use. i actually prefer topflite wood props but during the winter they break real easy.
so i put the 10x7 back on it when i got home. it did work on that 10x6 though.
i also have a 11x5 apc that im going to try. i think i have a 11x6 topflight that i might throw on their as well. well see
a while back i had a top flight 10x8 on it but it took quite a while to spool up.
(plane with the gms is a gp rapture)


would a topflight 11x4 be fine for that old magnum? (im worried i might be under proping it) its a magnum .40 GPA, a bushed engine. (on a spad stick)

Nothing wrong with these for sport flying if you are happy with them

ok everyone noone has hit the button except for Phoenixangel I am assuming that say a 13-6 is going to make the airplane faster than say a 16-6 am I correct

Yea 13x6 would be faster, more rpm same pitch = more speed. that being said, be careful not to let an engine over rev. A 10x7 on your 91 would probably unload at some ungodly rpm, but that would also likely be the last time .

Anything bigger than a 14 X 6 on a 91FX will make a real spool up dog out of it

w8ye is exactly correct. Look at the list of props I posted, anything less then 10000 rpm on the ground with a FX engine is just completely wasting a good engine.

Anything bigger than a 14 X 6 on a 91FX will make a real spool up dog out of it <- whats this mean i've seen it before

i guess i need to purchase a tachometer

There are many different engine configurations which produce differing amounts of power.

e.g. a 10x7 prop may be a bit too much for an O.S. .46LA but just right for an O.S. .46AX.

In the case of the GMS .47 it is just shy of the Tower Hobbies .46 in terms of power, but the latter is a real stump puller and I think just a hair more powerful than the AX .46, so a 10x7 is fine. On a lighter plane you may also get away with the 11x7, but the engine will need to unload in the air for effective RPM's.

I've never used that particular engine, but I assume that it is similiar to an OS LA .40.

An 11x4 may give you adecuate thrust for a .40 plane but it will fly somewhat slowly.

You may want to try a 10x6 instead.