So, I just recently got a new computer with Windows 8 and I transferred all of my save files from Ultima I through VI.
But I have a problem with Ultimas II- IV, even though my location, my party and everything else is as it should be, all of the boats that I collected through the journey in these games have disappeared. For example, on my old computer in Ultima III, I'm at the final place in the game in the game (Exodus' castle in the Isle of Fire) and my boat is at the entrance but on my new computer the boat just isn't there, effectively trapping me on the island. I have no idea why this is so. In Ultima IV I had like six boats waiting outside Lord British's castle but now none of them is there. Ultima V and VI have no problems whatsoever.

If anyone could help me it would be very much appreciated. Thanks in advance!

I'd suggest, assuming you still have access to all the files on your old computer, just copy and replace the entire game directory rather than just the save files.

If that's what you did, then I'm not sure how to fix this issue... at all. Sorry.

Thank you so much for your reply. But I figured it out on my own.So if in the future anyone has a similar problem to mine, this was the solution.

For Ultima IV you need both the PARTY.SAV and MONSTERS.SAV (both will have the date of your most recent save) for any ships you might have conquered, I guess because ships were previously hostile enemies. Those were the only two files I replaced in the entire directory of Ultima IV and it worked perfectly.

For Ultima III the following files are neccessary: ROSTER.ULT, PARTY.ULT, and SOSARIA.ULT. These too will have the date of your most recent save. I just checked this on my computer.

Ultima II I couldn't figure because I previously applied a patch and it has a lot of files, but I don't care about it any more.

I hope this is useful to someone in the future.

just finished a fresh playthrough of IV. a few times a ship i had very recently hopped off of vanished without obvious explanation. it seemed to coincide with landing within about 5 tiles of a towne or castle, and entering said location while there were monsters (not the sort that can sink ships and not in the appropriate orientation to do so even if they were) within a similar radius. this happened conspicuously with a few 'safety chests' too, like the one i customarily leave over the [REDACTED] patch in the Bloody [REDACTED].

it's not as simple as "limited number of things strewn around the landscape" either - the more ships i discarded along the shores, the less it happened, and larger 'paths of chests' persisted throughout the game. (come to think of it, they seemed to persist through hills more than over swamps - perhaps a more ecologically realistic script? ;) )