I have an Enya 90-4C engine but don't have a manual and can find precious little info online.
So I have a couple of questions.
1. what is the shaft size? Tower hobbies has the Enya 90-4S listed at 7x1mm (in trying to fit a prop I find it is just slightly larger than 1/4")
2. when using a prop nut like this [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXL751&P=7]PROP NUT[/link] . do I still need to use the washer? the reason I ask is the washer has a larger center hole and is centered by a flange on the nut that came with the engine so i would have no way of centering the washer and would have to buy one with a smaller center hole)
3. I plan on putting this engine in a Hanger 9 AT-6 any thoughts on this combo?

There are 25.4 mm per inch so 7mm is a mite larger than 1/4 inch. No you don't need a washer with the Higley prop thingie. (The brass ones are 'heavy hubs' but they aren't really hubs are they?) Be sure you have the right one for your engine. I've used the wrong one on an engine before. Did not work well.[]

You MUST use a locking prop nut with a 4 stroke engine....otherwise you'll never keep a prop on it!

Hi!
Locking nuts aren't necessary on a 4-stroke...only if you set it too lean it might be useful.
If you can set an engine ...you don't need any lock nut.

Regards!
Jan K
Sweden

I've never had a 4c backfire..... or a prop come lose....... But I never want to
find out or see what could happen if it did it at high throttle... So I "always" use
a double nut............................