dual portable gas tanks

[bob johnson]

I just boat a big aluminum boat . I got the tiller version because I wanted an open floor plan( small decks) but i bought the console extra to install myself. the boat still has a deck up front. I want to keep the stern as light as possible , so i want to put the batteries under the center console and the gas tank way up front.
the deck is enclosed for about 4 feet up front with the exception of the center 26" width. it is like a crawl space for storage.

I checked under some of the plastic plugs in the deck and I can see the flotation foam isnt much higher than the floor under those areas on each side under the deck.

I want to leave the center for storage and cut hatch openings in the face of the deck on either side of center to store a 6-9 gallon portable gas tanks. ONE ON EACH SIDE!!!

I need at least 12 gallons i figure. I want portable..not permanent..

I mix the oil with the gas..and i want to be able to pull the tank and empty if I have to for what ever reason.

now the delima

feeding the motor gas lines running under the flooring. Id want to run one gas can at a time( I THINK)

how can i do this?

run both to a Y fitting?

run to a shutoff switch to route one or the other to the motor?

do i just pull the quick dissconnect fitting on the empty when i go to the second tank?? and hope the O ring seals??

I have to stay with the quick dissconnect to keep the tanks portable...

but am open to ideas to feed my motor fuel and not create fuel delivery problems in the process


if you know of a product or products please tell me their name
thanks


bob

 

[timdan94]

Re: dual portable gas tanks

I always just swap by pulling the quick connect and moving to the other one. I've had no leaks yet. My dad has done it this way for about 30 years.

 

[bob johnson]

Re: dual portable gas tanks

I always just swap by pulling the quick connect and moving to the other one. I've had no leaks yet. My dad has done it this way for about 30 years.

I wont be able to. Each gas tank will be in its own compartment...and Id like to just leave it in there once it is full. with a line coming from under the floor to that compartment.

instead of pulling both tanks and switching and putting them back in the opposite hatches.

once under way and all my gear in laying in the boat...
I want to avoid a scene like that...

Id love to just trow a lever and close off one line and open the other from my console.

IF THAT IS POSSIBLE

bob

 

[clarkbre]

Re: dual portable gas tanks

Won't having one empty and one full make the boat lopsided? Anyways, I'd make a hose long enough to reach both tanks. You could leave them both in their given positions then just switch the hose from one side to the other. The only other alternative I can think of would be running 2 seperate lines from bow to stern and switching them at the engine.

In any event, unless you're running an electric fuel pump on each tank, you're going to have to do a manual switch of some sort.

 

[reelfishin]

Re: dual portable gas tanks

I just switch tanks as needed on my boats, I had a made up a Y configuration and fuel hoses but it was problematic and hard to keep pumped up. I had fuel feed issues with all that line and the valve. I did as stated above, finally, just ran two fuel lines, one from each tank to the motor and swap them when needed. The idea of running off of a right or left tank and emptying one then the other is an issue on some boats, but I just empty the starboard tank first, then the port tank, leaving about 1/3 in the starboard tank as my reserve.

Can you mount a single larger tank? How about a low profile 12 or 15 gallon tank?
I had a 12 gallon single tank which I used to drop under the one seat in my old boat, it was only about 7" tall or so. It was considered a portable, but it was hard to handle when full.

 

[bob johnson]

Re: dual portable gas tanks

Won't having one empty and one full make the boat lopsided? Anyways, I'd make a hose long enough to reach both tanks. You could leave them both in their given positions then just switch the hose from one side to the other. The only other alternative I can think of would be running 2 seperate lines from bow to stern and switching them at the engine.

In any event, unless you're running an electric fuel pump on each tank, you're going to have to do a manual switch of some sort.

shouldnt the boat is a 2070 aluminum Mod V...pretty stable and wide.

if keeping the lines full is an issue I could run a single line from each tank to my fuel seperator and have a quick disconnect right there...nice and solid and only one line running to the motor over the transom.

I just dont like the idea of the extra line not being used flopping around. we use the boat in severe winter...ice forms on a lot of stuff...

it would be my luck when i need the second tank the end is frozen solid.

plus i risk wearingout oil rings on the couplers...which might lead to fuel line issues...

id rather had a solid system up to the portable tanks..if possible

bob

 

[Chris1956]

Re: dual portable gas tanks

Bob, first of all two 6 gal plastic tanks in the transom will not affect the trim of a 20 foot boat, very much. You might try it to see if you can live with it. it will make your fuel solution a whole lot easier. Secondly, why not permanently install a single 12-18 gal above deck tank, and fill it via siphon hose from a 6 gal premix jerry can? That way you can fill it to the brim with fresh premix, and the jerry cans are pretty cheap (<$10Ea).

 

[Silvertip]

Re: dual portable gas tanks

Let's cover a few issues with dual tanks. 1) NEVER use an electric fuel pump on an engine and electrical system not designed for them. Why? Because electric fuel pumps will run anytime the key is on. A failure anywhere in the fuel system means the engine can be pumped full of fuel. EFI engines have an ECU that knows when the engine is running and will disable the pump if the engine dies. Carbed engines can use an electric pump but it must be powered through the oil pressure switch so if oil pressure drops (as in the engine dies) it kills the pump. To start the engine, it will have no oil pressure until it does start, you need to add a start bypass circuit. Carbed two stroke outboards have no oil pressure switch or any other means of shutting down the pump without building a custom electronic device to accomplish the shutdown. 2) You cannot simply "Y" two fuel tanks because they will not draw down at the same rate so one will always run out and therefore suck air before the other is empty. You can however, use a fuel selector valve (electric or manual) to switch tanks. It's done on trucks and has been done for decades. Install the valve between the tanks and the water separating fuel filter. Then a single line to the engine. You will likely need a primer bulb in each line before the filter as they work better "forcing" fuel through the fileter rather then "sucking" it through.

 

[bob johnson]

Re: dual portable gas tanks

Bob, first of all two 6 gal plastic tanks in the transom will not affect the trim of a 20 foot boat, very much. You might try it to see if you can live with it. it will make your fuel solution a whole lot easier. Secondly, why not permanently install a single 12-18 gal above deck tank, and fill it via siphon hose from a 6 gal premix jerry can? That way you can fill it to the brim with fresh premix, and the jerry cans are pretty cheap (<$10Ea).

thanks for the reply....

I realize boats are JUST boats for some people they are tools for others.

this boat needs to do a specific task, and the modifications I make to it are to helpt it do that better.

I want to be able to AT LEAST FLOAT this boat in very shallow water. I use it in tidal areas for hunting.
meaning we are not moving.. the boat sits for long periods..and during that time the tide can fall...the deeper the boat sits in the water...the shorter the periods of having to reposition it.

plus the greater the chance an unforeseen boulder under water becomes an impasse for leaving!!

so i dont care too much about how the boat trims...but i do care how shallow it can float...even if I have to hop out and walk it..the shallower the better.

the rear is were it has the most draft , so am doing all I can to get weight awat from the transom.
I had custom flotation pods weldedup in Fla to weld onto the transom to raise the boats at the rear.

12 gallons of gas weighs about 72 lbs!!

i have had days were I JUST ..JUST BARELY got my boat out of a tight spot by myself, over a bunch of rocks in the water, while i pushed and lifted and busted a you know what...if I had an extra 70 lbs in the back...i bet i wouldnt have made it. and id be stuck till the tide returned.

bob

 

[Chris1956]

Re: dual portable gas tanks

OK, Put a single 12-18 gal tank in the bow. Permanently mount it above the deck and siphon the fuel into it. It is still a simpler and more reliable solution that you proposed.

 

[bob johnson]

Re: dual portable gas tanks

OK, Put a single 12-18 gal tank in the bow. Permanently mount it above the deck and siphon the fuel into it. It is still a simpler and more reliable solution that you proposed.

I dont want anything to be up in the way especially a permanent 18 gallon tank. there are so many issues with bad gas...poorly mixed gas..old gas....gas with water...that you need to get rid of it...it is hard to if it is in a permanent tank...

I can easily get rid of gas from a portable tank...

secondly there isnt room for that big a tank...unless i use up the storage in the middle...it is a good place for my dog on the long cold wet rides back.

here is a picture . there will be center console on the boat...so it looks like a lot of room in the photo...but it wont be like this for long..

on either side of the opening up front, i want to cut two hatch openings with doors.
there is room for a 6-9 gallon tank... wont loose the surface area above..but ill get a convenient place to store the tanks out of the way...

thanks

bob

 

[CATransplant]

Re: dual portable gas tanks

How about building your center console to hold your portable tanks? That would pretty much solve the weight-distribution problem. Shorter run for the hoses, and you could access the tanks easily from the operator's position to swap fuel lines or whatever.

I wouldn't run flexible fuel lines from the bow to the stern, anyhow. If I had to make that long a run, I'd put rigid fuel lines under the deck and connect to them at both ends with flexible hoses.

 

[bob johnson]

Re: dual portable gas tanks

well CA,,, I already bought the console and it is premade..it is the factory CC...I got it all loose from the dealer. there is a live well/seat in front .

I like the idea of pushing the weight up front...

if rigid is better, I am all for doing it.

I found what looks to be a valave in west marine just for switching tanks.
anti-siphon....guess that means it wont pull gas back from the motor for any reason....towards the tank..

I am mounting the twin batteries under the CC anyway...plus ill have a little glove box type storage unit in there for important papers and such.


do you think id need ball inline up near the tanks in addition to the one Ill have between the fuel seperator and the motor?

is long runs of fuel a really big issue????

should i go bigger or smaller ID lines, because of the length

bob

 

[Silvertip]

Re: dual portable gas tanks

You need bigger lines the longer the run is. Decreasing the size means you starve the engine. As for selector valves, you need one of these (although there are valves that are less expensive.)

http://www.cpperformance.com/detail.aspx?ID=842

The anti siphon valve is only part of what you need in this system. If the fuel tank is higher than the carb in any boat you need anti siphon valve which is a fitting that installs at the outlet of the tank. This prevents fuel from flowing toward the engine not from the engine to the tank. A fuel selector valve is like a light switch -- it determines which tank you want to draw fuel from. There are both electric and manual versions.

As I explained earlier, the primer bulbs can be anywhere in the line between the tank and the fuel selector valve and you need one in each line going to the valve. A single bulb between the water separating fuel filter and the engine is not a good plan as they don't work well in that configuration.

 

[bob johnson]

Re: dual portable gas tanks

wow , someplace i saw a photo of a rigged motor with the primer bulb mounted withiin about 12" of the motor laying on all the other cables feeding the engine!! (it was actually ABOVE the transom!!!)

and it was stated that is the "way to rig a gas line"

so I was thinking that is where i should put my main one.

bob

 

[Silvertip]

Re: dual portable gas tanks

The primer bulb cannot suck fuel through a water separating fuel filter with any authority. It is much better at forcing fuel through this system. On a single tank setup with no water separating fuel filter, it can be located anywhere in the line. Make sure you know all of the details before looking at a picture and deciding this is correct for your installation. ANY engine these days should be fitted with a water separating fuel filter, especially if you own an EFI/DFI engine and even more importantly if you are required to run ethanol blended fuel. I'll say it again starting from the tank.
Fuel tank, anti siphon valve, primer bulb to fuel selector valve.
Same for second tank.
From fuel selector valve outlet to water separating fuel filter.
From water separating fuel filter to the engine.

You can certainly try a single bulb between the filter and the engine. If it works that's great, but most don't primarily because of the filter and the length of the line involved.

 

[bob johnson]

Re: dual portable gas tanks

great thanks....but this is the first i heard of a need for an anti-siphon valve.

i mentioned before that the fuel SELECTOR also had a anti-siphon feature!!

does the gas tank itself( moeller top side) have this anti-siphon design?

or is this just one more thing I should buy to make my boats a pleasure and not a headache..because i am all for buying these things now while I am in there doing the work.


as for the bulb between the seperator and the engine...it wasnt an idea I had...it was just something that was stated in another thread , and a picture was offered as further explaination...

I guess it doesnt means its the best way..

thanks again

bob

 

[Silvertip]

Re: dual portable gas tanks

Anti siphon valves are typically installed directly at the tank. That way any leak in the line between it and the engine does not pose a siphon problem. I've not seen a portable tank that had an anti siphon valve. But that doesn't mean one is not needed.

 

[jay_merrill]

Re: dual portable gas tanks

I have a 17.5 foot boat with a two permanently installed, 12 gallon saddle tanks. I also have a fuel line running forward to the self bailing deck in front of my windshield. This line is used to access fuel in a pair of plastic 12 gallon aux tanks that I can put in the boat when I need them. The fuel lines are standard rubber, CG approved lines and they meet at a 4-way valve (off, left, right, forward), right next to the steering station.

Each of the permanently installed saddle tanks has a primer bulb at the tank. The line running to the foredeck does not. I also have a fuel/water separator downstream of the selector valve, between it and the motor. The line between the separator and the motor also has a bulb, which is located at the motor.

I can prime my lines from any of the bulbs. I have had no trouble priming the system from the engine bulb, all the way from one of the bow tanks, through the valve and separator to the engine. The bulb pulls fuel through an empty separator canister just fine. I perform SAR missions for the USCG on a semi-regular basis and use the aux tanks for extended range, when I do. Since my system has been used many times with those aux tanks,as well as the main tanks, I feel confident in the viability of the layout.

There are many ways to set up such a system and all have their benefits and limitations. As long as you recognize what those benefits and limitations are, you'll be fine. If you decide to go with rubber lines all the way, just bear in mind that they need to be inspected periodically. This is also true of tubing, because it can crack due to vibration. If you do decide to run lines below deck, be sure that you have full access to them for inspections.

BTW, if you can put one or more tanks in the center seat shown in your photo, you might want to consider that as an option. I recommend this simply because forward tanks have a disadvantage, in that the trim of the boat will change as fuel is consumed. When possible, a center mounting position is preferable. That said, if you can't do it, you can't do it. Using the system with the tanks up front just becomes a matter of getting used to different handling characteristics with varying fuel loads.

 

[Mark42]

Re: dual portable gas tanks

Install the two portable tanks, and connect each tank to a 3-way valve, then a single line from the 3-way to the back of the boat. The 3-way valve is on-off-on, so you can choose which tank to draw from, or shut them all off. You can't really see it it the pic, but there are two mounting ears on the back side of the valve to bolt it to a bulkhead, etc. Get 3 hose barbs to connect the hoses to the valve. I have this valve on two boats and it works great.

I understand your reluctance to use a permanent tank, but I do think its not as big an issue as you may think. Small permanent tanks in the 12-18 gallon size generally have no partitions, easy to syphon empty, and so far, I have not seen any buildup of gunk in tank.

Check out these two links where I put small permanent tanks in my boats, and note the use of the 3-way, and also in-line water separating filters:

17 gallon tank job: http://shareaproject.com/pages/projectTut,p,503,00.html

14 gallon tank job: http://shareaproject.com/pages/projectTut,p,78,00.html


It sure beats lugging around portable tanks. Pull in the gas station, fill it up and go.

At any rate, the 3-way will solve your portable tank issues.