I had an ST .61 2S mounted on my Bird Dog which was destroyed by a broken piston-not worth fixing. I just bought a Lipo charger to use with a couple of EDF units I'm playing with. Haven't gotten any batteries yet. Question is what size electric motor would it take to equal the output of the .61. Thinking this might might be the plane to try electric since it thas plenty of room inside. Also, outrunner or inrunner? The motor designations leave me scratching my head trying to figure how one converts. Thanks for any thoughts, Bill.

I use an AXi 4120-14 to replace the .61 2S in several scale aircraft. I use 22.2 volts and a 12 X 8 prop and a 70ESC and the power and time in the air is just perfect. This combo pulls around a 12 pound PT-19 85 inch wingspan with ease. Also have combo in a 81' 7 pound Cub. Norm

You are definitely going to want to go with an outrunner. More power and torque for the heavier planes, and just plain easier to deal with.

Here are some other options to look at:

Great Planes RimFire 42-60-600

HiMax HC5018-530

Axi 4120-18

E-Flite Power 46

Thanks for the input, guys. I have a CC Phoenix 60A ESC at this point, which I guess would be adequate for now. I had just assumed the inrunners were easier to mount. See what I mean: if there's a pattern to the designation of each motor, I'm too dumb to see it!

Yes, inrunners are easier to mount and some of the more expensive ones are equal in power to the outrunners, but power to weight ratio goes hands down to the out runners. NOrm

Yup, all manuf. pretty much have their own numbering system. The only one that makes good sense to me is the RimFire - 42 is the dia. in mm - 60 is the length in mm - and 600 is the kv rating.

How do you know what prop to use with the 42-60-600?

On the tower site, they recommend a range of props.