Originally Posted by bogbeagle
Well, if it were mine, I'd be tempted to get some soft-ish wire and form it such that it fits into that groove, thus preventing the prop driver from moving back along the crankshaft. Seizing wire or even copper wire should do the trick. As you suggest, the prop driver will prevent the wire from "popping out" of the groove.
Do not know about those elder types of wire circlips like used on Ohlson piston axles and on their car wheel retainers (quite hard to remove) but a large good quality spring steel circlip should do the trick no ?