I'll probably be dogpiled giving this some serious thought but what the hell...It's been a question in my mind for a long time....

The time is drawing near that I need to make a decision on what to do about my aft fuel tank mod. Ive had the bed off the frame for a year and I need to either do the mod or slap the old "in-cab" tank back in. For a long time, Ive had the idea of using a good quality plastic boat tank mounted back between the rails aft of the rear axle. They come in a lot of dimensions and Ive certainly found it hard to find an ideal automotive tank that fits easily in that tight little area. The mustang tank mod that everyone suggests just doesnt look like a good idea to me. I refuse to relocate or remove the frame cross-members to accommodate and it still looks like a painfully close fit.

Today, I found a plastic boat tank at West Marine that looks like it will fit perfectly in that bay although there may be a little trimming on the cross-members' bottom flange just to get it to nest a tad higher in the bay.

Am I missing something or is there no good reason a guy couldnt or shouldnt use this tank?

It's a 12 Gallon, Low Profile and it appears I could feed it thru a hole in the bed simple enough. And I might even be able to come out of the tank and do a 90* elbow to go to a fill location forward or aft of the tank.

It has a built in sight gauge on the top. And I'd say a person could remove it and install a sender that would work with a dash mounted gauge. Or to keep it simple...could just use the sight gauge.

From what Ive read, modern plastic tanks have a lot of safety advantages over metal ones. In fact, my F350 has a big 39 gallon plastic tank for the "stove oil" my 7.3 burns. Plastic seems to be more resilient in an accident and has no corrosion issues or seams to crack and leak. Plastic also has some give for thermal expansion (although the cap is ventilated too).

I think I'd make sure the plastic tank made good contact with the frame someplace so as to avoid static electricity sparks. And I also think I'd weld up some sort of steel "shield" to keep road debris and exhaust heat off of the tank.

https://www.westmarine.com/buy/west-...37?recordNum=4

 

I would do it in a heartbeat. I have suggested it before. Only thing you need to watch is the sending unit ohms so the gauge works properly.

 

Might be another option. Don't know anything bout it though.

http://www.parts123.com/parts123/yb....Z5Z5Z50001018c

 

12 gallon seems a little small to me.

 

Well....12 is a little small. But the space we have in that bay is tight. There is a deeper version of that tank but it's taller and might hang too low.

I will be running on either the original 240 or a 300 six. So hopefully my MPG wont be down in the single digits. And it's just a local driver not a work truck or trip truck.

 

Thinking about trying to tweak the arm on the original sending unit to get a cockpit indication. Otherwise, I'd probably just keep an eye on the sight gauge thru the fill hole in the bed.

 

You can probably get away with it in the bush but here in the big city in Canada any uncertified tank for road use would be a no no. So long as johnny law is not going to look I say go for it!

 

I have considered that issue because we are planning to move across the border to Yukon CA next year. Ive read that vehicles imported to CA have to be inspected and figured Id have to make sure the original tank was installed for the occasion. Funny how safety regulations sometimes prevent improvements in safety. My background is in aircraft maintenance and that is a common thing.

So, I wonder if installing an automotive gas tank back between the frame rails would still be a no no just because it's a modified fuel system?

And I suppose if you had any kind of accident while running a boat tank, it would automatically be "a contributing factor" and I'd be in deep ****. Ultimately, I want to do what is safest because the truck will belong to my 11 yr old son some day.

 

The only reason I would do a rear tank is if I either wanted 2 tanks, or I wanted more room in the cab for storage. I have never in my entire life heard of an incident involving an in cab tank. #1 if there is a leak , you will immediatly smell it when you get in the cab, and #2 if you get hit hard enough to rupture the tank, you are already dead before it has time to ignite.

 

Welcome to Canada! Yes usually there is an out of country inspection that needs to be done. Your vehicle is better off being stock but they don't mind upgrades such as seat belts and reverse lights. As far goes a marine gas tank that has never been tested for road use would likely fail inspection due to liabilities in the event of an accident. Another consideration is the lack of baffles in a marine tank. Sloshing on a boat is less noticeable than a vehicle on solid ground. Once your in the Yukon I doubt they will care to much as it is sparsely populated and they are happy to have someone live there lol. I have never been to the Yukon and every province/territory will have different rules. My best advise is to shop now for a shop to do the inspection and also contact the Motor Vehicle Branch and find out what is needed.

RMM

 

My main motivation is to open up some space behind the seat. Im not that concerned with the tank behind the seat being a safety hazard. If you notice, the cab tank is mounted on top of an extremely husky "box beam" that runs the width of the cab. It's probably the toughest structure on the whole truck.

As for flammability, this truck has been thoroughly tested. The original owner smoked a pipe in it every day for the 1st 40 yrs of it's life.

 

Thanks for the welcome. My wife is Canadian and she's wondered for years why we stay in this increasingly dysfunctional country. The only reason Ive held out is that I love Alaska. But even Alaska is getting too crowded for me (if you can believe that). Fishing and hunting up here have become "elbow to elbow" social events anymore!

It's almost comedy that it's perfectly legal and acceptable for me to fill that boat tank with gas and sling it in the back of the truck and drive around 24/7/356 without even strapping it down. But If I secure it with straps and run a hose to the engine, it suddenly becomes dangerous.

On the subject of baffles....I dont know if that is even an issue. Ive never seen inside a car fuel tank that has baffles. I know my 2000 F350 has none. It's just a big plastic box. My guess is that anti-sloshing is provided by the shapes and indentations in the shell of the tank itself...both boat and cars.

 

You make a point about the tank in the box. You would have to have it strapped in most places in Canada because you are not supposed to have loose cargo in the back that could come flying out in an accident. Yukon probably won't give a crap, its usually reserved for the more populated areas. I think the fuel modification laws are more for preventing trying to get better fuel economy by installing fuel vapourizors. It's only an issue during an inspection to get into the country or to another province/territory or after a wreck to prove fault. You could technically drive for decades without a licence and never get caught. I actually knew a guy who drove his own tow truck for 16 years without a valid licence. People just assume you are legit if you have a name on the side of your truck lol.

 

Prior owner of my 65 F100 Styleside installed axillary tanks on both sides between the rear fenders and the forward part and below the bed? On the passenger side he gutted the tool storage compartment and brackets leaving the door. He then installed 24"x17"x6" aluminum tanks on both sides and cut fuel access doors and ran a 3" inlet pipe thru the bed side panels and then cut an opening in the bed floor and connected them to the tank.Perhaps with the side tanks setting lower than the cab tank poses a problem filling the tank but seems to me one should be able to come up with a better design?? At the time is was not an issue because I originally purchased the truck for parts but later decided to keep it and now in the process, when time permits, removing tanks, access doors then patching.

 

My truck came with those saddle tanks just as you describe. Im doing away with them tho. They stuck down so far they were visible. and the doors are ugly on the side of the bed. And they really arent protected by any heavy structure...just the bed sheet metal.