As I recall those hoses are more likely to be 5/16" i.d. but you can always take one apart and measure it.

If your hoses are of the crimped-ferrule type, they're a bit more difficult to reproduce. Otherwise you can just get some replacement marine-grade fuel hose, cut some new pieces, and have at it.

Crimped hoses can be done, here's a bunch of info from the Mercury Outpost archives on the ferrules and crimping tools for that:

fiberglassics.com/forum/search.html?query=ferrule&searchdate=all&searchatdate=04/17/2024&childforums=1&catids=17

Here's an inexpensive crimping tool for 1/4" and 5/16" fuel line ferrules, other sizes are available as well:

www.amazon.com/Interstate-Pneumatics-H6-V-Grip-Crimper/dp/B0093JOLCW

The advantage over that NOS set you found, is that the NOS hoses may not be alcohol-resistant. Important nowadays unless you've got a reliable supply of non-alcohol fuel.

Plus once you've bought the crimper and ferrules and any special fittings you need, you're well-equipped to make more fuel lines on any other old Merc. A good investment if you're planning on digging into the hobby further!