Anyone know what size spinner to use on a 46fx os engine being used in an Aircore Colt 40. (40 size plane) This is not in the manual.

Spinner size is usually determined by the cowl size not engine size. I don't think your plane has a cowl so I'd suggest a
2 to 2 1/2 inch spinner. About right for that engine anyway.
Dennis-

The more I read the more I see what you mean.
thanks Dennis

Like Dennis said, pick one that looks good. This is the only case where size DOESN'T matter.

Tom

I have an OS 46 FX with 11 x 6 prop, was using a 2" but recently moved to a 2 1/4" because I found it much easier to fit (still had to trim the openings for the prop to fit though - is that normal?).

Dave

thanks guys! I ordered a 2 1/2" from Tower.
Shipping is getting out of hand there though.

Yes, trimming the opening is normal.
You do not want the spinner to touch the prop.
Just try to trim even amounts from both sides.
I use 2 1/4 spinners on my 46's.

Bill

Maybe I won't have to trim the 2 1/2" spinner but after putting together an Aircore Colt, I"ll at least have plenty experience with the trimming part!