I hope I don't regret buying a starter based on the old starter in the boat..... The old starter started the boat and it spun it the right way but didn't always want to engage so I bought a new one based on the chamfers on the starter gear (there is information on the Arco site about how to identify which rotation is needed). I guess I need to throw the battery in and test it, I would be pretty upset if the PO put a new (but incorrect) gear on the starter...
The other possibility is that due to the different year and model of our boats the starters are mounted differently, but the engine spins the same way. If the gear is facing forwards on the driver side vs backwards you would need an opposite rotation.
Best of luck!
1986 Supra Sunsport Skier with 351W and swivel spotters seat