Fuel Tank Return Line

[chichiflys]

I replaced the aging and leaking 30 gal aluminum tank on our '82 H36 last week with a 14gal Moeller plastic tank. It was the largest I could fit in the space where the original was (had to cut it out). Turns out I can actually fit another 14 gallon tank on the same shelf, and I may do that but would need to build in a way to transfer fuel....definitely possible, but not necessary at the moment as I can fit three 5-gallon jugs of fuel in the remaining space on the shelf forward of the new tank....I digress.
The Moeller tank does not come with a return line already plumbed. I know I can replace the fuel sender with a universal type that includes a built-in return line port, but that's another $75 on top of the $390 tank (which by the way are hard to find in stock, 12-16 week wait if not in stock) - so I found a brass Tee, 5/8"x5/16"x5/8" that I can insert in the tank's vent line, then slim down the 5/16" barb to 1/4" with a reducing barb for the 1/4" return line from the engine. Anyone sees any issues with this arrangement? The Kubota V1505 we installed doesn't seem to return a ton of fuel (I currently have it plumbed into a small 3-gallon jug, but that is a temp arrangement)....and I would think since the vent is much larger at 5/8" ID, there should still be plenty of air that can get by to vent the tank. Thoughts?

 

[Ralph Johnstone]

WOW ! First of all, B E A U T I F U L photo shots and parts layout of your plans. Couldn't be clearer. I'm compelled to say this because of the endless questions that are posted here on an almost daily basis and consist of a brief session (even worse is a long session) of incoherent babbling that leaves the reader completely in the dark. Ask them for a photo of the problem and they disappear like a wisp of smoke, never to be heard from again. I suppose it is a lot to ask.

Having worked on my own poly fuel tank for a few items, I'd like to suggest reducing barbed fittings to only the last one and going with threaded fittings which will also allow you to stay away from the vent line. You're thoughts on flow will work but best to have a separate tank attachment for each individual line. If you do say "Damn the torpedoes and stick with the vent line" use threaded fittings in the catalogue and avoid the barbed fittings where possible.

A separate tank attachment should be quite simple but here is a catalogue you may find useful for fittings. This is the manufacturer I buy from but the catalogue is too big to slip through here so you'll have to download your own :

file:///C:/Users/Owner/Downloads/flipbook.pdf

Fairview is big so you'll likely find a supplier in your backyard.

For one tank attachment, I simply made this which is used for sampling fuel :

A couple of thoughts when dealing with poly, only use Permatex #2 as a sealant as it is the only thing I know that permanently sticks to poly :

For threaded pipe fittings, use a couple of wraps of teflon tape and then a light coating of Permatex #2 over the tape. This is guaranteed to seal against diesel fuel.

Show us how you intend to connect this up once you have the time to filter through the fittings to see what is the best selection for your needs.

 

[chichiflys]

Hi Ralph - thank you for the kind words and thoughtful reply. Of course it's a bit late as I made the change before checking the forum! So for now I'm going to run some more tests and see how this works out. Perhaps when time and other projects allow, I'll remove the kludgey arrangement and either install a dedicated port into the tank or replace the fuel sending unit with one that has a return fitting incorporated. Here is pic of the current setup; I ran the engine today with no immediate issues. I decided to replace the 1/4" ID return line with a 5/16" ID line to avoid having to install the reducer and two more hose clamps prior to the T-fitting. But it's still too many hose clamps for my liking.
I'd like to avoid all the hose barbs as you mentioned, however the link to the catalogue you recommended didn't work (I think it's a path to your hard drive) - what is the name of the manufacturer and I'll google and then download a copy from their website... Although I suppose McMaster Carr probably has what you recommend. For now though I think this is a temporary but workable solution, with room for refinement down the road. Thanks again!

PS - Looking at this picture I wonder if the engine control panel wiring being so close to the fuel tank is really a great idea? it's pretty much how the original arrangement was set up - but something tells me it's likely not an arrangement that would be "approved" by any Marine certifying organization?

 

[Ralph Johnstone]

however the link to the catalogue you recommended didn't work (I think it's a path to your hard drive) - what is the name of the manufacturer and I'll google and then download a copy from their website.

That's exactly what it is. Must have been half asleep when I put that in there. The company you want for a good catalogue is Fairview Fittings. You may find what you want in there to tidy up the install.

PS - Looking at this picture I wonder if the engine control panel wiring being so close to the fuel tank is really a great idea?

I don't know if it presents a danger seeing as how diesel fuel has such a low flammability. As long as the area is reasonably well ventilated, I wouldn't think it presents a danger although somehow I doubt that ABYC would approve.