What exactly keeps the spinner nut in place when using an electric starter?? I'm pretty sure that the starter rotation turns the same direction as removing the nut.

Eh, the lock-nut?

I have one on most of my planes...

Lock-nut?? Are we thinking the same thing?? Here is a link:

http://www.shopatron.com/product/par...161.5188.0.0.0

Friction!!!!! I've uesd one of those nuts for years. If you tighten it properly it won't come loose when using your electric starter.

If it's tight, the starter will not spin it off.

No not a spinner nut...

Rather a seperate lock nut like this

http://www2.towerhobbies.com/cgi-bin...?&I=LXL761&P=7

( search for Higley's on Tower ).

I use these extensively for 4 strokers and sometimes on two strokers.

On 2 strokers merely cranking the prop nut as tight as possible with a 6"-7" wrench will work.

On four strokers a lock nut is needed.