Fuel Line Sizes

[Attikos]

For the Yanmar 3GM30F on Sequoyah, 1/4" rubber fuel line is installed. I don't know how long it's been there. It came with the boat. It appears to be getting a little long in the tooth, though, so I'm going to replace it.

Is there anything wrong with going to 5/16" line? Judging from their specs, the filters could handle it with no trouble. If it delivers more diesel to the return line, then it seems to me it would only improve the polishing effect as the excess fuel flows through the system and back to the tank.

Has anyone looked into this question before?

[Jammer]

I end up switching line sizes -- 3/16 1/4 5/16 3/8 -- fairly often when replacing line. It is really more a matter of what is at hand, what will match the fittings, and what will fit, than anything else.

Any of these will flow far more fuel than any auxiliary engine will use. The spec for 1/4" line is like 15 GPH or something.

[Attikos]

Thanks, Jammer. Appreciate the experienced advice!

[DeepFrz]

I'd recommend using 5/16" from tank to filter including the fuel pickup. Less likely to get a plugged fuel line that way. Of course, having experienced a clogged fuel line in a seaway I'm a little gun shy on 1/4" lines from the tank.

[Attikos]

DeepFrz, something similar is actually what motivated me to think about larger line. When I got this boat it had been neglected for a couple of years. The fuel was dirty as a politician. Did my best to clean it up, took the boat out on a glorious day with fifteen to twenty knot wind, ran up the sails and cut the motor, had a great few hours that later showed to have sloshed the diesel around in the tank and turned up plenty of sediment I missed. Needless to say it was a tricky business getting back into port, what with the motor smoking, overheating and all. I want to do all I can to avoid a recurrence of that.

[Jammer]

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.

[Attikos]

I've wondered about that. I never hear farmers complain about fuel fouling, and most of the ones I know keep their equipment less well than I do my boat. Their farms are in the humid, warm South, too. Not much different than a marina. There must be a reason.

I'll look at the possibility of a hard line between tank and first filter. Thanks.