The 4-stroke F200 thru 250 have scattered reports of internal exhaust corrosion when used in saltwater. Most are from 2002 to 2005 and have high hours but not all of them. It would be a good idea to have a trained Yamaha tech check out any used motor that has seen saltwater duty.
The seller told me he has replaced them, and told me it is a big problem, the boat is a good deal but I just wanted to check it out im in fresh water in the river and trailor to the ocean. Thanks