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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Fuel line diameter

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C25BC
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Canada
200 Posts

Initially Posted - 01/22/2019 : 21:01:43

Picked up a new fuel line for my 8hp Yamaha the other day and noticed when I got home the diameter is 6mm , it looks quite a bit narrower then my old one .
What size is optimum ?

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

islander
Master Marine Consultant

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3992 Posts

Response Posted - 01/23/2019 : 05:26:00

I'm not sure about optimum but a 6mm line will supply more than enough fuel than your engine could use. For instance Volkswagen and my old Honda 9.9 used 6mm fuel line.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Voyager
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USA
5231 Posts

Response Posted - 01/23/2019 : 20:14:01

In my case I bought some new fuel line that was the same O.D. as my current line. When I went to replace my line I found out that the I.D. was a gauge smaller than my fittings. I tried squeezing it onto the hose barbs but no dice. I tookit back to the boating store and the clerk explained that since the advent of E10 and E15, fuel lines have changed substantially. They have multiple layers and so the O.D. is proportionately larger than before.
The moral of the story is to measure your fuel line hose barb diameter and purchase the right size fuel line. No point wasting time.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

C25BC
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Canada
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Response Posted - 01/24/2019 : 07:18:05

Thanks for the input , I couldn't seem find any info from Yamaha and didn't know if a larger I.D would some how increase performance.

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 01/24/2019 : 16:28:49

Just a heads up and is what most guys forget about but changing the tank to engine fuel line in an attempt to stay ahead of trouble is a false sense of security. What most don't do is change the fuel lines under the cowling that go from the fuel connector to the fuel pump then from the pump to the carb. I bet most here have never changed them ever. Weak link in the Chain. I changed mine on my Honda and am sure they were original from 97. It's how I found out they were 6mm. Putting a larger tank to engine hose won't do any good because the smallest fuel hose in the entire fuel line is 6mm.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

C25BC
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Canada
200 Posts

Response Posted - 01/24/2019 : 18:27:41

That's good to know , I'm taking it in for the spring service soon . The only reason I'm changing exterior is because the old on failed .

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

Voyager
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USA
5231 Posts

Response Posted - 01/26/2019 : 16:49:42

Scott, your logic is impeccable. That�s a very good point.
I changed out the internal fuel filter once in 2009 and again in 2013. Since the internal fuel line looked good and it did not break off in my hand, my assumption was that it was perfectly fine. In my case, the external fuel line was attacked by the sun�s UV rays and that made it brittle, that�s why I changed my line.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 01/26/2019 16:51:43

redeye
Master Marine Consultant

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3474 Posts

Response Posted - 01/27/2019 : 20:23:37

<fuel line under the cowling >

well I don't know if thats the weak link... I've found it was the o-ring in the quick disconnect fitting.

I've changed out the line on several engines after finding the line split at a fitting after something like 10 years. But that was line made many years ago.

Todays fuel line I've bought has been problematic to me ... the "many Layers" and outer layer exposed to the sun has broken down quickly.

I bought some rather expensive grey colored fuel line from the marine dealer and the relatively clear "plastic" layer inside the line appeared a bit brittle after 3 years.

Im not using e10 or 15 gas so Ive gone back to using 3/8 in black line I've found at Auto parts stores that is "old Style" line and SS hose clamps. Seems like nothing is "standard" anymore and every time I look for a part it is made differently with every batch.... anyhoo wish me luck.

I'm sorry I don't know what Yammys are using. I've read they are good engines and used a lot up north commercially... outlasting many other brands.

Please don't hesitate to let us know your findings with your yammy fuel line replacement.

Ray in Atlanta, Ga.
"Lee Key" '84 Catalina 25
Standard Rig / Fin Keel

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.