Is there a standard fuel hose size?

[Country Dirt Kid]

I am looking to buy a fuel tank hose and primer bulb assembly for a 18 hp 1980 Mercury. I can barely read the markings (3/8) on my old sun baked hose. Most of the hoses I see sold online say 5/16. What I don't understand is whether or not this is an outer or inner diameter. Is it like there are two different O.D but the same I.D. Help is appreciated. My calipers are at work and work is closed because of quarantine. Thanks for the help.

 

[roscoe]

5/16 ID hose will work fine for an 18 hp.
3/8 will work too.

But what size is the hose barb you are attaching to?

 

[Texasmark]

5/16 feeds my 115 hp, ought to feed your 18.

 

[Chris1956]

As Roscoe said, smaller motors use smaller fuel lines. 1/4" fuel line is OK for smaller motors, like yours. 5/16" fuel line is OK for up to about 115HP or so. 3/8" fuel line for 150/175 HP and 1/2" for larger motors.

I would find out what fits your motor and replace with same.

 

[Faztbullet]

Only buy OEM ...Attwwod and Wallyworld stuff is junk

 

[Texasmark]

Only buy OEM ...Attwwod and Wallyworld stuff is junk

On that subject sir, what are the symptoms? Does the OEM have the same (modified diamond shape) as the old one, or has the EPA messed things up to the point that they all look like a football and doubled the price and are sloppy pumpers?

Edit: Just answered my question: https://www.amazon.com/QuickSilver-8..._t2_B00FM90VXU.

And that one is a sorry pumper like the old football aftermarkets of the past.

 

[jimmbo]

Until the Summer of 75, all the fuel lines were 5/16" Flowed enough to feed the 150hp of the day. When the V6s were introduced, they needed more fuel than the 5/16" could deliver, so 3/8" was introduced for the V6s

 

[Faztbullet]

Uhh ...Tex that one you posted is a OEM EPA ethanol bulb with DUAL check valves..it and Yammys are best on market.

 

[Country Dirt Kid]

Thanks for the replies. I measured the brass hose barb that connects to the engine with calipers and the biggest part of the barb is .40" and the smallest part is .35" If I convert those to fractions it doesn't match up with any specs on any hose.

 

[Chris1956]

What is the inside diameter of the fitting? Likely .25

 

[Country Dirt Kid]

What is the inside diameter of the fitting? Likely .25

That's exactly what it is?