I think it would he highly unusual for a dealer to offer a warranty on a pre-owned boat, but you never know. Most are going to be sold as-is and it's up to you to do the inspection and arrange for a compression check, or have a knowledgeable friend go with you.
2015 Seaark 1872 MV CC Etec-90
Two Helix 12 CHIRP SI's, , MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
2018 Robalo R180 CC, Yamaha 115
Bitter Gun Owner