Most foils stall at between 15 and 20 degrees angle of attack. Of course
that is measured from the chord of the foil to the fluid flow, so when the
boat is rotating the flow is across the transom rather than along the keel.
Once the blade stalls, you could pretty well replace it with a bucket or sea
anchor.

Someone mentioned prop wash. I must admit I keep thinking sail boats.
Prop wash, engine thrust, there may be reasons for turning the rudder
further, but it would be for low speed maneuvering. (???)

Roger

http://home.insightbb.com/~derbyrm

"Chris" wrote in message
ups.com...
(Not knowing the boat) I would guess that 45 degrees is plenty. I have a
tiller, which would allow 180 degrees, and I think I rarely ever use
more than 30.