reb181jr

Hi all new kid on the block...lol just bought a 1996 256 (first boat) with a 351w motor with volvo penta out drive dual prop  ...won't turn over  my mechanic and I are looking into the possible causes... the story I got is the owner died and his wife just left in on the trailer for 6 years and then sold it it ran the last time they took it out it's in really great shape clean and everything works looked in the cylinders with borescope and they are in good shape also the plugs looked great burning clean. we have put ATF in the cylinders and are letting it sit for a week( we think it's the rings) any suggestion are welcome. Thanks