I just received a sach 3.7 motor for my 1/4 scale hanger 9 232 and I haven't a clue of what size prop to put on it as this is my first 1/4 scale and first gas engine. I was hoping someone here has a similar plane.or knowledge to help me as props for these engines are expensive and I can't afford to go through to many
Thanks:

3.7 sounds like it could turn a 22x10. Might try a 22x8. Is that a magneto ignition motor?

Yes it is a magneto ignition done by Brisson

That thing may weigh enough that you can mount the servos in the tail. That thing is going to be landing really fast.

Thats a lot of engine for the 25% H9 Cap 232.

Maybe you should look for a 35--40cc engine for it. That 3.7 is about 60cc!!! You could use that on a 28% plane with an 80--90" wingspan.

I'm not sure your going to like the way the little 25% Cap flies with that heavy of an engine up front.

I flew my H9 Cap with a ST3000 at 6000' elevation and it was a monster. It weighed 11.75 pounds and would hover at about 3/4 throttle. Pretty darn good when you read the posted weight of a lot of the H9 Caps.

I really wouldn't put that much engine on that plane if I were you. Trust me--I'm all about HP and hovering. Too much HP is just about right. You DON'T have to fly it at full throttle. With that engine on the firewall---you'd better not fly it at ful throttle. You'll rip it apart. You've got a pretty darn heavy engine there, and you could easily get the Cap to hover and fly 3D very well with an engine that weighed significantly less.

Save the 3.7 for an 80"+ plane and get a 35--45cc engine for the 25% Cap.

I had a Saito 180 in mine. I should've put a Moki 1.80 or a gasser in it. Probably would've put some kind of 40cc engine. It's comes out extremely tail heavy and can be a pain if there's a crosswind. That was my experience at least. Now i'm flying a Wild Hare 120 Edge with a OS 160. Great combination.

brisson 2.4 is plenty of engine and still to big of an engine for the plane in my opinion. Mine has a os1.6 and flies better overall.

Holly crap!!!!! did I read this right a 3.7 in a h9 72in. cap, are you sure you dont mean the 80 in. cap. I had a 46cc poulan chainsaw in mine then took it out for a 30cc stihl on glow engine and it was a better flier with the 30cc stihl, the one pictured in my avitar. If it is the 72in. I would seriously reconsider your choice or engines.

Darin