Anyone retrofitted an inernal fule tank into a boat

Charlie,

I checked a few local welding shops. The big shop refused to do it because of liability, (they said).

The best small shop around was pretty pricey but probably would have done the best job He was going to heliarc weld the tank but would only take the job on a per hour basis.

The shop I went with had a reputation for getting the job done for a good price. They used a wire fed welder ( I forget the correct terminology, Mig or Tig or something like that.)
The tank was not pretty but has held up well with over a decade of men and dogs stepping on it while picking up decoys in rough water.
I showed them the space I wanted the tank to occupy and requested 18 gallon fuel capacity. As I stated earlier the tank ended up holding 24 gallon. If space is critical you might want to determine size and capacity yourself before turning the welder loose.
I also asked for a baffle to be welded in the middle to keep the fuel from sloshing around.
They forgot to put one in but I've never really noticed the need for one in actual use.

The tank is made from 1/4" aluminum treadplate and has held up fine.
In hind site I might have went for the heliarc welded tank and the better craftsman but the tank has held up fine and being made of 1/4" aluminum could be easily rewelded by a competent welder if need be.

I chose the location of the tank based on the characteristics of my particular boat. It was light on the front end and would porpoise if not heavily loaded.

The fuel separator is critical to using this big of a tank in my opinion. When I empty the filter every fall there is water in the bottom of the filter.
I bought it from west marine and it uses a mercruiser screw on filter. I just stop in to the dealer and buy a new one every year.
The filter is mounted inside a storage box welded to the boat ribs.

Mike
 
A couple more thoughts.

The choice of 1/4" aluminum was made with the thought that the tank was really going to take a beating up in the bow of the boat and I did not want to split a seam on a rough day.
I also used a rubber mount to cushion the tank.

I'm not an engineer and don't know what grade of aluminum would be best suited for this but there are a lot of aluminum treadplate fuel tanks being installed in the bed of pickup trucks.

Mike
 
Paul, Mike,

Thanks!

Mike, I think wirefeed is generally MIG/GMAW welding (TIG/GTAW uses a tungsten electrode and you feed the filler rod in manually). I took a welding class at the local trade school and have done a bunch of MIG welding on my old race car. I've done MIG and TIG, and also gas welded some, if I had any sack I'd try to weld up a tank myself, but I'd hate to foul up something important holding explosive gasses.

I'll definitely run a fuel/water separator. I've been meaning to do this for years anyway, so now is as good a time as any to start. Seems like good insurance, especially with the increasing amounts of ethanol they're putting in fuels.

Paul, if you do find some pics, I'd live to see them. I've been looking for used/NOS, etc, but no luck so far. I'll keep looking. OEM would be ideal, but plan B is to fab up what I need, except the filler, vent, hoses and clamps.

Thanks,
Charlie
 
Charlie go for it. 1/4 " aluminum is definitely better than the plastic tanks most use. As long as your welds are bright and shiny your good to go. Plus you will get exactly what you want. Use tag board mock up and use it for your pattern. Personally if you have access to a tig welder thats the way I would go.
 
Charlie, One quick word on water seperators. Make sure that you get one that will not restrict the fuel due to being too small. When alchol started showing up in fuel some guys added a seperator that didn't have the flow capacity and seriously leaned out their engines. I think they only come in a couple sizes so just get the right one and you should be good to go. I run one on my fishing boat (75 hp.) but not on the smaller ones. I just use a small portable tank for them and watch for water. Good luck.
 
Tom,

Thanks, I'll keep an eye out as I shop for them. I looked at two styles, one marketed under the SeaSense brand and another from Moeller with a water drain. The Moeller was twice as costly. I think they both had 3/8" ports.

Charlie
 
If you can find one that plugs right into your side locker that's obviously gonna be the easiest/fastest way to get to where you're going. But if you don't run across something, don't be afraid to take it on yourself. With even a little welding know-how you can put it together. When you think you have it done just pressure check it. If you see any bubbles fire the welder back up... no big deal. Tig would be the way to go if you have one at your disposal. I've used the aluminum guns on the mig welder too and they do a decent job as well.

Made one for the front of a 16 Alaskan w/ a 50 4stroke tiller and it balanced it out great. It ended up a hair smaller than the doghouse, and as near as I can figure, held about 13 gallons.
 
Charlie, I to have a 16ft Lund. Been looking for a replacement tank for awhile now. After the season over I'm going to open up the rod locker and built a custom tank. Have you made any progess in this area? Looks like a mig and spoolgun are my next big purchase. West Marine has a fill/vent comb in their catalog that should work.

Mike
 
Hi Mike,

Last I thought about it, I'm going down the custom route. Millematic 180 and spoolmate 100 spool gun are on my shopping list. Unfortunatley it is too cold in VT to 1) weld aluminum in my garage and 2) get the boat out of the snowbank to make a template.

Here are some things to think about if you do make one:

The tanks needs baffles every 30" with openings at the top for air and the bottom for fuel. Minimum .090" thick material (per AYBC H-24) and minimum .25" thick on small passenger carrying vessels [46 CFR 182.440, table 182.440(a)(1)]. Fittings should be manufactured out of alloys 5083, 5086, 6061, 6063 or 300 series stainless. All openings must be at the top. Vent should be at the high point in the tank. Must be designed to prevent standing water from sitting on top. Tank cannot be integral with the hull or be used to support any hull structure or deck. All threaded tank fittings must be tapered pipe thread (NPT). It will need to securely mounted and also be electrically bonded to the hull.

The book I have says that there are restrictions on placing tanks in the bow unless the tank as met certain rigid test standards.

The tank will need provisions for fill, vent, supply lines and a level sensor. Min ID for fill is 1 1/8", min ID for vent is 7/16". Leve sensor should be a two wire marine unit.

Secure all connections with two stainless steel hose clamps (screw type, USCG does not allow spring type).

Pressure test to 3 psi or to a head of fuel equal to a 1.5x the maximum distance from the lowest point to the highest point in the system (vent or fill).

Moeller makes a fill/vent kit. I'm sure there are others too.

Oh, and don't forget an external filter/water separator.

Here is one place that makes custom tanks: http://www.sptanks.com/webdev/home.htm

Let me know how it goes if you pull the trigger first.

Charlie
 
I think it is going to need to be roughly like this...

I can't remember how deep it is, and it is in a snow bank under cover so I can't go measure.

Charlie

tankpic.JPG

I hate math, but if I am anywhere in the ballpark, those dimensions (if 13" deep) would give me 17+ gallons, and I could keep half of my storage locker open for other stuff.
 
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I hate math, but if I am anywhere in the ballpark, those dimensions (if 13" deep) would give me 17+ gallons, and I could keep half of my storage locker open for other stuff.
Click to expand...

Wow... I don't know your boat, but if it's a smaller version of mine, I don't see how you can get that much fuel...

well, according to a few calculations, you're in the ballpark with the dim's you provided.... make sure your fittings fit in the space and that you're not maxing out the tank and forgetting the space required for the filler neck attachment, hose bib, etc.
 
Paul,

The '97 might be a little different, but the 18' is essentially the same as the 20' in '99 - two feet shorter, but not exactly sure where they chop the 2' - I think they may take it at the transom area.

My '99 has two square anchor lockers forward of the side bulkheads (just in front of where the console goes) that I didn't see on your photos of the 20. They also got rid of that diagonal brace in that area (the area was probably stiffened by the boxes).

Does this look anything like what Lund used for the filler:

[inline [font=Verdana,Arial,Helvetica]gasfill.jpg]

This one is made (distributed) by Seachoice. [/font][font=Verdana,Arial,Helvetica]It has an integral vent with flame arrestor. And it is under $20. [/font][font=Verdana,Arial,Helvetica]I think it is what I am going to use.
[/font][font=Verdana,Arial,Helvetica]
I'm thinking I'll get a metal shop in Burlington to make me a shroud to hide the filler neck. Probably have them roll it round it like the newer style ones, and then hit it with grey zolotone when I spray the interior metalwork.[/font][font=Verdana,Arial,Helvetica][/font][font=Verdana,Arial,Helvetica]
[/font][font=Verdana,Arial,Helvetica]
Charlie
[/font]
(oops, forgot, no spaces in file name....)

fill.jpg
 
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