Fuel fill, feed, and vent sizes on Tank

[rothfm]

Hi all,

I figured out my Tank size on another thread...But a last question seemed to get buried in it. Starting for Seperate question.

Are Marine Tank fittings standard? Meaning Fill, feed and vent? Got a good used tank and found a local welder that can
fix me up, providing I get the Bungs, fittings needed.

Boat is a Tiara Pursuit 2600, Twin 150 Johnsons. Seems like standard stuff but not 100% what to purchase. Not sure looking at original either.

pics large pics attached.

OH, also...in the picture of the orig fuel pick valves...What part is the anti-siphon? Those are 90degrees, with a shuttoff valve and then a barb.

Really appreciate the help, as always

Thanks

 

[dingbat]

Fill is 1-1/2”
Fuel outlets are 3/8 npt- 3/8” is fuel hose
Vent is 5/8”

Doesn’t appear to be fitted with an anti-siphon devices. Outboards don’t require them

 

[rothfm]

Dingbat, thanks alot! Appreciated...

Today I crawled into covered boat to see the Supply hose is 3/8. Stupid question on the 3/8...is the "bung" that I have to purchase for the welder to install, also 3/8...Guess it doesnt matter long as the final barb is 3/8.

Appreciate it!

 

[dingbat]

Stupid question on the 3/8...is the "bung" that I have to purchase for the welder to install, also 3/8...Guess it doesnt matter long as the final barb is 3/8.

I would base the fitting size on the availability of the shut off valves.

While 1/2” to 3/8” hose adaptors are common place, 1/2” fuel shut off valves may not.

 

[Bondo]

Stupid question on the 3/8...is the "bung" that I have to purchase for the welder to install, also 3/8...Guess it doesnt matter long as the final barb is 3/8.

Ayuh,....... I've seen 1/4" pipe bungs, 3/8" pipe bungs, 'n 1/2" pipe bungs used, then adapted to, usually 3/8" lines, or 1/2" lines on huge horsepowered boats,.....

 

[Chris1956]

Each of your engines needs a 3/8" fuel line. Anything less can cause a lean condition which is bad. I recommend water separators as well.

You could run a single 5/8" fuel line and single high capacity water separator(40GPH).

Vent lines are typically the same diameter as the fuel lines, although they do not need to be as large.

Built in tanks usually come with anti-siphon valves. Anytime there is a risk that a fuel line could leak (or break), where the leaky/broken end of it is lower than the fuel level in the tank, a siphon could occur dumping fuel into the bilge. Hence the requirement for an anti-siphon valve.

What is the need for shut-off valves? They can leak, and if you never use them, why have them?

 

[dingbat]

You could run a single 5/8" fuel line and single high capacity water separator?

Except you loose the redundant fuel supplies to each motor.

Been there, done that.

 

[Scott Danforth]

Vent lines are 5/8" ID (USCG standard is 9/16" minimum to meet the 2 GPM rule). Since they dont make 9/16" hose, 5/8" is the norm
Fill lines are 1-1/2" typically for gasoline and 2" for diesel
fuel lines are typically 3/8" ID in a 1/4" NPT fitting until you get over 500hp

 

[Chris1956]

Except you loose the redundant fuel supplies to each motor.

Been there, done that.

OK Dingbat, I'll bite. what are the advantages of dual fuel pickups, lines and separators, on a single fuel tank feeding two motors?

 

[rothfm]

Thanks all. I got into the boat again...Agreed, the feed lines are 3/8, the vent neck appears to be 5/8, and the fill line not marked but appears to be 1 1/2.

Heres a pic of one of the fittings I got off the top of the tank-- Of course unscrewing this, it appears it left the stuck feed tube in the bung. Owell, they are all getting replaced anyway!

Everything seem like its like this: 3/8 Brass Barb, to 1/4 shuttoff Valve (male one side, female other ) the 90deg fitting bottom looks larger, Not sure what that is, maybe 1/2. That is the part that actually goes into the bung I believe, Not sure cuz it left a threaded part in the bung.

I'm going to keep seperate feeds to ensure good supply volume. Could eliminate the shuttoffs I guess as they will always be on , but can see any issue having them.

I also have 2 254gal saddle tanks next to the main 100gal..Those also have this same fitting setup. They feed individule lines to a 4 port large fuel filter, with 2 output lines going to the motors.

Thanks all. Once figured out, I can purchase what I need, and bring it all to the welder.

 

[rothfm]

ok, Just did some research...I believe I could use an Aluminum bung of 3/8 npt. Seems alot of the Feed Tube assemblies out there are for 3/8. They then have a 1/4 NPT female side to use a 1/4 to 3/8 barb for the hose.

Think I got it...

Question, the aftermarket pickup screw in tubes all appear to be plastic, and I'm seeing complaints of quick rotting or breaking.

Why Not an Aluminum tube..Or rubber fuel line made for inside tanks?

 

[rothfm]

Even better, I can re-use my original barbs, Valves and 90deg elbow, then enters the tank at 3/8....Sweet.

Now just the question of the actual pickup Tube,,,Universal/Generic? I'm skiddish of the reviews of Moeller and others failing, is there such thing as a solid Alum tube, rubber?

Almost there,

Thanks all!

 

[rothfm]