Fixing gas tanks. Please help!

[Dubbies]

Ok so I have this metal tank I'd love to use because if fits perfectly for my boat. 90 litres so it's almost 2 times bigger than another plastic one that I bought that's 50 litres.

Here are my options. Which one would you pick?

1) metal tank but it's a bit dirty. the guy had it in his boat a month before I bought it. My plan is to put a bit of gas in it, put a new chain in there and swish it around for a bit. Try to take some rust/debris out from the bottom of the tank. Empty it, and repeat the process until it's not getting any cleaner.

Or:

2) use this plastic tank that doesn't fit as well in the boat and only holds 50 litres. I'd have to cut some holes in it and vent it, screw in the fittings from the old tank (hopefully I cut it right because I only have one chance) and just live with it being a little in the walk way and not having as much gas on board.

What should I choose? Option 1 or option 2?

 

[messabout]

You can reclaim the tank using the chain and sloshing method. You can also use bolts and nuts, nails, or even clean pebbles. Much sloshing will be required. The tank may or may not have so much iron oxide deterioration that it could be unwise to use it. Hopefully it is not seriously damaged. When you are satisfied that the interior of the tank is sufficiently cleaned, coat the interior with the gook that is designed for that purpose. You can find this at automotive parts stores..... or who knows, maybe even Amazon. The idea is to coat the interior metal surfaces with a protective barrier that can discourage rust .

I believe that you can find You Tube articles that describe this process.

 

[Dubbies]

Thanks so much for the reply. I really appreciate it.

Yah, I looked on YouTube for a long time and only found one guy showing how to clean it properly. I'll try cleaning the inside of it and give it a go. Hopefully it's still good. The guy was using it a month before I got it in his boat so I'm hoping it's still ok to use.

Any tips on what to use to clean it? Alcohol? Sea foam?

 

[SolGato]

Agree that you should clean the metal tank and use it. Doesn’t look bad at all to me. Just use gasoline.

If you can gain enough access, fashion yourself a scrubbing brush mounted to the end of an extension and try to reach the areas you can see before doing a general sloshing with chain.

I never recommend coating a tank if you can avoid it.

Then just make sure you have good fuel filtration.

Install one in the tank at the pickup if possible, or at least a sock, and another inline upstream.

Try to avoid using Ethanol gas. Ethanol is hygroscopic and will absorb water which can lead to further corrosion.

 

[Dubbies]

Agree that you should clean the metal tank and use it. Doesn’t look bad at all to me. Just use gasoline.

If you can gain enough access, fashion yourself a scrubbing brush mounted to the end of an extension and try to reach the areas you can see before doing a general sloshing with chain.

I never recommend coating a tank if you can avoid it.

Then just make sure you have good fuel filtration.

Install one in the tank at the pickup if possible, or at least a sock, and another inline upstream.

Try to avoid using Ethanol gas. Ethanol is hygroscopic and will absorb water which can lead to further corrosion.

Thanks so much for taking the time to respond.

Why should I not coat it?

It had a filter in the pickup, I think I can put it back in.

I've never put one in the fuel line to the motor. Can anyone refer to a good one off amazon for me? I know they're hit or miss.

Also, how do I ground the tank? What part of the tank shpuld I ground to the transom?

 

[fallguy]

I'd never slosh metal parts in a steel can with gas in it.

I seem to recall a fellow online who used denatured alcohol to clean the tank. He also used mek.

 

[Barry]

Also, how do I ground the tank? What part of the tank shpuld I ground to the transom?

The ground should be to the engine/neg side of the battery and more than likely the filler cap

 

[Dubbies]

Yah sorry I meant swish it around with the chain and then do the gas to wash it out separately. I don't want to risk a spark.

Ok so I need to run two lines to ground it? One tk the negative on the battery and one to the filler cap? What if my filler cap is plastic?

Also, where would I run one to the engine?

 

[fallguy]

The ground to the filler cap is to prevent a static spark. So, yes, ground any metal cap (with a clamp or other) to the tank ground then the common bus on the boat. Nothing needed for all plastic cap. But for your tank a ground is needed on a metal tank for static.

An electronic sender also needs to be wired. It is common to run a tank ground and a sender ground as in the picture I added, but make sure the tank ground has continuity to the tank.

If you have an outboard, all grounds end up at the starter battery negative terminal.

If you have an inboard; the engine(s) must also be grounded. An outboard is grounded via the starting cables.

hope this helps

 

[Barry]

Yah sorry I meant swish it around with the chain and then do the gas to wash it out separately. I don't want to risk a spark.

Ok so I need to run two lines to ground it? One tk the negative on the battery and one to the filler cap? What if my filler cap is plastic?

Also, where would I run one to the engine?

You should be ok not to ground the filler cap if it is plastic BUT it might be worth checking into that with the coast guard. It was not too many years ago that they found that a plastic gas can
could build up static electricity if it was not grounded. A stretch with a small cap but??
The engine will be grounded to the negative side of the battery.

 

[Dubbies]

Ok so with a plastic filler cap and a plastic tank, I just have to run a word from the tank to the negative port on the battery?

 

[gonzo]

You should pressure test the tank first. It may be full of pinholes.

 

[messabout]

Pressure test with very low pressure only. Be sure of the cap gasket so that you do not get a false reading. If you suspect a leak, use soapy water applied with a paint brush to explore any suspicious places. If bubbles develop, you have a leak.

 

[Barry]

Yah sorry I meant swish it around with the chain and then do the gas to wash it out separately. I don't want to risk a spark.

Ok so I need to run two lines to ground it? One tk the negative on the battery and one to the filler cap? What if my filler cap is plastic?

Also, where would I run one to the engine?

ABYC
24.15.1.1 Metallic components not in contact with the fuel (eg retaining chain and/or cap) or non-metallic deck fill assemblies shall not be grounded.
24.15.1 Each metal or metallic plated component of the fuel system and tank which is in contact with the fuel shall be grounded so that its resistance to the boats ground
is less than one ohm. A metal fuel cap is part of fuel system

I could not find a specfic clause that states "that you have to or do not have to ground a plastic fuel tank" Rather, if it is metal the grounding requirements have to be met
Note that if you install a stainless screw through the metal sending unit flange, the screw will in essence ground the tank. See below

11.16.1 If a DC grounding system is installed, the DC grounding conductor shall be used to connect metallic non-current-carrying parts of those direct current devices identified
in 11.15.2.1 to the engine negative terminal or bus ,,,,,,,,,,, to ensure a fault current path in the event of a short

11.15.2.1--1 For liquid level gauge transmitters installed on conductive surfaces, ie metal tank, ---- shall have the transmitter negative return conductor connected DIRECTLY to the
DC main negative bus, the engine negative terminal, (outboards to the battery neg/bus) NO OTHER DEVICE SHALL BE CONNECTED TO THIS CONDUCTOR
EXCEPTION: Isolated sending units that are isolated from the static grounding and bonding system. (Which a plastic tank would be unless it is bonded/grounded)
NOTES: This conductor may also serve as the static ground and/or the bonding connector for the tank and fill (but it appears that a plastic filler is exempt)

 

[Barry]

Pressure test with very low pressure only. Be sure of the cap gasket so that you do not get a false reading. If you suspect a leak, use soapy water applied with a paint brush to explore any suspicious places. If bubbles develop, you have a leak.

Great point, ABYC states 3psi