Well, if you're replacing suction line, think at least as hard about material and fittings as you do about diameter.
I'd rather have 1/4" hard line (steel) than, say, 3/8" rubber hose.
I'd rather have fittings that make a positive connection, than a piece of hose jammed over a piece of hard line with a worm-drive hose clamp over it. At a minimum, use the clamps that tighten with a screw and nut. They don't work
over as wide a range of sizes, but they clamp much tighter.
I used to farm and had diesel tractors and skid loaders, and worked on neighbor's combines, and I must say we never seemed to have nearly as much trouble with fuel contamination as occurs in yachts. Even though the combines sit under a tree 11 months a year. My most serious fuel problem was with #2 diesel gelling when I got stuck with the wrong fuel in the tank when the weather
got cold. The only contamination problem I had was with a tractor where the fuel outlet in the tank was blocked due to pieces of plastic that were left in the tank during manufacturing.
I filled everything from my own bulk tank and had a filter and water
separator on it, which I replaced every few years (whether it needed it or not), and the engines had the stock fuel filters and water
separators, usually a couple of them, but fuel was never the problem. Getting the tractor with the snowblower on it to start when it was -10 degrees was the problem. Ended up installing a dispenser that would deliver a measured shot of a mixture of ether and liquid propane
into a nozzle in the intake manifold while starting, worked great.
Anyway, buy clean fuel, keep it clean, use hard line where you can and rubber where you have to, turn over your fuel supply a couple times a year, you'll be fine.