Hi ESa
The Honda Marine Carburetion Manual is very vague as to this question and, at one point refers you to a "Marine Model Chronology Publication" to match serial numbers with part number applications. I've never seen one of those books.
But, maybe this will help you:
According to the Honda Marine Carburetion Manuals that I have, the first four digits of the flange code are the most important and the last four digits "have no service purpose"....whatever that means.
Example:
A BF50 AX model outboard would have a carburetor ID of...BG31B C...any digits stamped after that don't apply.
The first four digits give you carburetor type and horsepower ie: BG is carb type (found stamped on the carb near the flange number) and 31 the code for 50hp.
I'm sorry, but I could not find what the C stands for but I'll keep looking.
As to your question about the 35 hp, the 45 hp and the 50 hp outboard flange codes they are listed like this:
35hp=only one listing....Carb ID....
BG12A B with the number 12 indicating 35hp.
45hp=only one listing....Carb ID....
BG15A B with the 15 indicating 45hp...
50hp=two listings based on outboard frame number. Carb ID....
BG31B C and
BG31C E with the 31 indicating for use on 50hp engines.
I'm not sure this answers your question but it's the only info I currently have.
Hope I haven't just confused you more.
Good luck.
