126driver:
Lumpy,
Pull the gears and check everything out. That way you'll know for sure what's going on with the box. Click on the banner above and email Tom at Menkens. He'll hook you up with a prop. Probably 11.5 x 15 or something like that.Ditto, Tom at Menkens is the guy to talk and the best source of parts for your v-drive. He even sells my bearing puller so you might as well get it through him (same price even).
His props are not cheep but who's prop is these days. If you buy a new prop from him, he will make sure you get the right prop on your boat. Just ask Snowboat how Tom helped him with props.
If I'm guessing I bet a 15% gear and something in the 11.5X15 pitch range.