I have a wood prop that is 13 x 5. Can I use that on a .61 engine? The manual recommends an 11 x 7, or 12 x 6 to begin with.

It's a little large for a break-in prop but can be used after you get some running time on the engine.All you need is ground clearance for it. Max

I would go with what the manual states. A 13 inch might be to much for your engine. Good Luck, Dave

My Thunder Tiger .61 did not like the 13x5 at all. It ran pretty well, not great, with 11x7, 12x6, and 13x4.
My ASP .61 runs great with a 12x6 and I have never tried anything different on it.
Both are two strokes. My brother uses 12x6 on his ASP .61 four stroke.

It depends on the particular engine. I ran a 12x5 on my .46AX, once it was well broken in, and it LOVED it. 13x5 was a lot for my .55AX when it was new, but probably would have worked into it over time.

Hi!
Should not be a problem!

Like Jaka I see no problem at all but prop choice is a personal thing. You may or may not like how the prop/engine/plane combo works for you, the pilot. Most people new to the hobby can't tell if the do or don't like a set up, as long as the plane fly's they are happy with it. I know the first couple of years I was flying I didn't understand prop selection at all. Now days I may spend days testing props.