fuel system plumbing

Joined
Jul 22, 2012
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Hey all, so here's an update on my 1966 starcraft 18' with a mercruiser 110 i/o. I have finished installing new gauges and tach. Have my new depth finderer installed. I have straps made for my free 18gal marine fuel tank and got motor running perfect.
Now for the question. The previous owner had a 6gal portable fuel tank in the boat and im mou.ting a 18gal fuel tank i got for free in the bow due to the jump seats i bought will not work properly otherwise. My logic says to plumb hard line with rubber lines on ends for freedom of flexing. I have asked several marine shops about this but get no definate yes thats a great idea or no, bad idea. Whats the concensous here. Hard line with rubber flex ends or complete rubber line from tank to engine pump.

Also, can i rebuild my engine mounted fuel pump????? Im old school. Rebuild instead of buying replacement.
 
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roscoe

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Re: fuel system plumbing

Fuel pump, yes, rebuildable. Don't think Mercury sells the kit any more, but since this is a GM L4 153 Iron Duke engine, you can get the parts.

I would prefer rubber fuel line, as you could remove it and inspect or replace it. It would be pretty difficult to replace the hard metal line without ripping up the floor.

I would run a 1,5" pvc pipe under the floor to serve as a conduit to hold the rubber hose.
 
Joined
Jul 22, 2012
Messages
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Re: fuel system plumbing

If i did the hard line route, i wouldnt mount it under floor, was thinking under the side rails where it is easily accessable if it needed to be serviced. Tank will be above the floor, not under.
 

jbcurt00

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Re: fuel system plumbing

Use proper flexible marine gas line, I didn't find any references for a hard line marine fuel line. Do you have a supplier for hard marine fuel lines?

Boats don't behave like cars, and are subjected to different conditions then cars. A boat fuel line requires other considerations beyond 'just' fuel delivery. The USCG requires marine rated fuel hose, for both fill & feed, for a reason.

Although flexible line can be breached, it'd be less likely to be damaged in many situations where hard lines would be.
 

CheapboatKev

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Re: fuel system plumbing

I agree on the rubber lines, again make sure it's MARINE rated fuel line.
If you want to go metal, you have to get the right diameter brake line, use a bender then flange tool on the ends
Seems a PITA
 

heyyou325

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Feb 17, 2011
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Re: fuel system plumbing

A little tip for the line is to get a clear one. If you see air bubbles, you're sucking air, and you can also see the condition of the fuel. I just had a piece of gunk (off the side of the tank I guess) plug my selector valve, and since I had fuel before it, but not after it was easy to fix.
 

grzzzz

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Re: fuel system plumbing

Hmmm I have not seen clear CG approved/marine rated fuel lines? Would be nice if there was. The only "con" I can think of for using a combination of flexible and hard line is you will have 2 additional .... probable leak points. And, chances are at some point in the boats life they will leak. I don't know where you live or how active your "inspectors" are at your docs but they check my fuel system lines every year here in NM before they put on my annual inspection sticker. Lines must have the CG ID clearly marked and all connection double clamped.

Good luck!! I have a 66-67 Holiday,

Grzzzz
 

barato2

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Re: fuel system plumbing

Grzz, that's interesting. they must be more stringent up in Los alamos; they never even looked at my boat in Las Cruces.

agree that i don't think there is any clear USCG-rated fuel line. i'd also tend to just run rubber fuel line rather than use a hard section. if you do this, though, don't use brake tubing....Summit Racing sells 5/16" stainless fuel line which i use a lot for EFI conversions....good stuff, affordable, easy to bend without kinking.
 

heyyou325

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Re: fuel system plumbing

I'd have to check my old receipts, but I believe Summit Racing sold me some 3/8 clear marine lfuel line last spring. A month or two ago I got some 5/16 off Amazon advertised as marine grade. It was recommended by a local marina and the same as the Sheriff's marine patrol uses. Their mechanic gave me the tip to use clear line when possible. I do think I only used one clamp per fitting. Never really looked the reg up here. Oh, it passed inspection here too.
 

barato2

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Re: fuel system plumbing

on fuel system issues, i don't care if NO ONE is ever going to inspect my boat; those regs are there to keep you from blowing self up, or dying of 4th degree burns over 110% of your body, not high on my list of preferred ways to go. if you can get clear MARINE rated line, by all means go for it. but the real marine rated stuff has the poop to that effect printed on it; don't go by what the seller claims even if the local cops do use it.
 

grzzzz

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Re: fuel system plumbing

You are so correct Barato, burning to death surrounded by water.... a painful irony. I think it makes a difference if the water is state or federal operated. Lakes that are federal (typically power generator dams) are operated by the Arm Corps of Engineers thus you get to deal with the Coast Guard and their rules and not just state park rangers and fish and game.

Grzzz
 

barato2

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Re: fuel system plumbing

last i heard, the laws of physics work the same everywhere, state or federal lake. i'm building my fuel system to USCG regs altho boat will be in Mexico and not likely to run into any Coasties.
 

CheapboatKev

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Re: fuel system plumbing

Mexican Navy boat inspections consist of machine guns and no sudden movements.
 

Peter Eikenberry

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Re: fuel system plumbing

I spent many years enforcing the fuel system regulation. (I'm retired Coast Guard) In over 40 years I have never seen clear USCG rated gasoline fuel lines, except on PWCs. And the stuff used on PWCs is not intended for or allowed to be used on other boats. As was stated USCG rated fuel hose is required to be labeled USCG Type A1-15 or B1, and also today it will say SAE J1527 and may also have an ISO rating. If it isn't labeled go somewhere else. The exception is Aeroquip Racing Hose, but it will have a tag on it with the appropriate labels.

However, your question abut hard line is interesting. Metal lines are allowed but rarely used except on the engine itself. Mercuisers come to mind. Many of them have steel lines from the pump to the carb. However there are specific rules for metal lines just as there are for hose.
Sec. 183.538 Metallic fuel line materials. Each metallic fuel line connecting the fuel tank with the fuel inlet connection on the engine must:
(a) Be made of seamless annealed copper, nickel copper, or copper-nickel; and
(b) Except for corrugated flexible fuel line, have a minimum wall thickness of 0.029 inches.
Sec. 183.562 Metallic fuel lines.
(a) Each metallic fuel line that is mounted to the boat structure must be connected to the engine by a flexible fuel line.
(b) Each metallic fuel line must be attached to the boat's structure within four inches of its connection to a flexible fuel line.

see New Boatbuilders Home Page - Fuel Systems
New Boatbuilders Home Page* - 33 CFR Subpart J Fuel Systems
Or see Fuel Systems - Introduction

This stuff ain't cheap and hose is far easier to obtain and snake through the boat. It is also easily removed.
 

barato2

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Re: fuel system plumbing

wow. thanks for that info. guess that's the definitive word from soneone who knows what they're talking about. i'm curious though as to why they allow copper line but not stainless.
 

Peter Eikenberry

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Re: fuel system plumbing

Why not stainless? My memory fails me (senior moment) on that one but I will talk to some people I know and find out why.
Seamless annealed copper is not pure copper, and neither are the other two. Copper alloys are allowed but pure copper is not because it reacts with other metals, such as aluminum, and cracks easily. It is very susceptible to vibration, and as we all know boats vibrate. Copper has a very poor record on boats.
 

Peter Eikenberry

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Re: fuel system plumbing

Eureka, suddenly my brain is working again! Stainless Steel is prohibited for fuel lines because of a Crevice Corrosion. Contrary to popular myth stainless is not corrosion proof and the most common type of corrosion with SS is crevice Corrosion. What makes stainless stainless is an oxide on the surface, just like aluminum and various other metals have an oxide on the surface, that you can't see, but it is there and protects them from corrosion. This oxide requires oxygen to form. However SS is subject to vibration (like copper) and can develop small stress fractures (crevices) that are barely visible to the naked eye,but water or moisture can get in and exclude the oxygen, and corrosion sets in. Once the corrosion starts it continues until the metal fails. This is especially true of thin walled tubing like that which would be used for fuel lines.

Oh yeah, I forgot to add SS can also create galvanic corrosion with dissimilar metals especially aluminum.
 
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barato2

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Re: fuel system plumbing

i knew about the last part, altho that would be far worse with copper alloys than with SS. and now i recall that other bit about SS corroding in confined areas.....Nigel Calder talks about it in his book. thanks for that reminder.

bottom line, sounds like we all agree, use proper rated hose rather than hard line. Kum By Ya and stuff. :)
 
Joined
Jul 22, 2012
Messages
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Re: fuel system plumbing

Ok, so plumb rubber uscg a1-15 fuel line tank to pump. Is the concensous to use pvc pipe as a conduit. Fyi, decided under floor was better idea for plumbing system.
 

barato2

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Re: fuel system plumbing

honestly, whatever works. the factory uses an aluminum "tray" to support wires and stuff under the floor in the center consoles. i ran real NM (grey PVC) electrical conduit on one side and leftover PVC drain pipe (which i'd gotten an ebay rod in) on the other. i see no reason why the "real" conduuit is any better. just be sure it's well supported from the stringers (flotation foam will also help support weight of conduit, but don't rely on this alone) and has some sort of chafing protection where it enters and exits. drain holes in the bottom of conduit are a good idea.
 
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