hi Chris
Happy to have been of help.
You're right about the year-port-ship boxes for BT 98. However I think you only learn the name of the ship when you match the rotation number that's written on the form for the ship when you then get the name. So it's a case of starting at the beginning and looking at each one. There is little likelihood that the low numbers will match ships whose names are in the early part of the alphabet. It's a good thing that there's only one film and you've got Maryport not LIverpool
Can't recall where you are but unless you can take yourself off to London, ordering the film in through the nearest LDS (Mormon) church is probably your best bet. Ihave checed the catalogue for 1845 and the film number is as follows. It should cost you about $5 or L3 to order in each film
BT 98/729 Maryport A-Z 1845
Film
905430 To find the film numbers for the other entries you have you can follow this procedure:
www.familysearch.orgLibrary
Library catalogue
Keyword search -"Board of Trade"
Entries will come up -I have BT 98 coming up at entry 125 of 125 (2nd page of list)
YOu then click on this which takes you to the reference info. Click again on the top right (film details)
YOu will be horrified by the 5000 odd films from which you need to find yours.
I find it easiest to go to the bottom of the page , on the left, where you can enter a film number. Take a guess till you're in the right year range then you can work your way through the alphabet.
For example I found the Maryport one above at around 1050. Obviously the later the year, the higher film number you'll be looking for.
If the film has to come in from Salt Lake City (because no one else in your country has ordered it) then it can take a few months. However the good thing is that these are popular records so are usually held in the national repository locally. So unless someone else has it to look through then you shouldn't have to wait too long
All sounds convoluted but really isn't. I haven't used BT 98 but have found images from my ancestor's seamen's tickets on other batches.
Hope this isn't as clear as mud. If it is let me know
Pauleen