Surprised there hasn't been more discussion in this thread.
Here is a document that shows the USCG requirements:
https://www.uscgboating.org/assets/1/As ... 002.01.pdfThis covered EVERYTHING in the gas installation though, including tanks, tank testing and vent systems. What I really like about it is some discussion about WHY certain requirements are in there. The hose requirements start at about page 80.
If I understand the requirements, you basically need an "A" rated hose if it's in an engine compartment, or can use a "B" rated hose if it's not in an engine compartment. You can use a "2" rated hose (i.e, A-2) if it only used as a fill hose or vent hose (that does not really have liquid gas sitting in it all the time) and must use a "1" rated hose (i.e, A-1 or B-1) if it does have fuel sitting in it all the time, such as the lines to the fuel filters and to the engine. Newer hoses add a -15 to the end because that specifies a lower permeation rate on the hose to meet newer EPA regulations. I think most hoses you buy now probably already have that.
Here's a couple other good links with some clarifying info:
https://www.boats.com/reviews/confusion ... e-numbers/https://www.boats.com/on-the-water/what ... ings-mean/