Fuel tank

Lee Hadjiosif · May 13, 2013

vizwhiz said:
Considering building a custom fuel tank to fit a certain space on the outside of the boat. One side will have to be curved to follow the contour of the area it will fit. Any suggestions about material? Stainless? Aluminum? Fiberglass?
Also, is there anywhere that construction guidelines exist that tell you what a fuel tank has to have to be considered safe by the coast guard (and insurance providers), such as certain type of caps, vents, etc?

Aluminum is fine, but stainless is better but much more expensive and would be an overkill on your boat. All you need is a fill and vent lines on one side of the top and a supply threaded coupling and a return barb on the other top side. You would need to thread a tube in the supply coupling so it would draw from as close to the bottom as possible cut on a 45. I would also suggest a drain valve at the bottom of the tank so you can drain any dirt and water once in a while. I would not use fiberglass for fuel. Make sure you have enough flanges welded for fastening to the boat. Good luck.
Lee

MrBill_FLL · May 14, 2013

AFAIK, marine tanks don't draw from the bottom like on cars. Most fuel pickups are ~1/4" from the bottom of the tank, so you don't pickup sediment. its also why you want to know the usable fuel amt not the tank capacity. (can be 5-10% difference on large tanks. )
you want to hang it off the back of the boat? why not in the laz with venting? I can understand a propane tank, but not fuel... plus its weight up high.

FourPoints · May 14, 2013

Coast guard rules require no openings below the top surface of the tank if using gasoline. I just went through the whole process this year.

http://sailingit.com/blog/boat-projects/fuel-system-part-1

Sumner · May 14, 2013

I agree with MrBill that if you are going to go to the expensive of having a tank made, probably not cheap buy one similar, could be smaller, to what we used and put it in the laz.

If you only want 2-3 gallons then how about just over the outboard well for one that small and just use a commercial tank?

You can end up doing a lot of motoring where you are and 2-3 gallons is 18 to 30 miles max. and I'd want a little more reserve than that. From up in Tampa Bay to down by the pass to the Gulf is about 20 miles one way. You sail down there the winds aren't right or dark is coming on and you want to motor back. You might be cutting it thin on gas,

Sum

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MrBill_FLL · May 14, 2013

How about you get a little 2.5 gal tank and put it between the seats, put a box over it and go sailing....

some mac 25's have done nice jobs.
a quick fix is cut the bottom of a cooler out and put it over the tank...
makes a little table and drink holder.

or add a swim platform and put it on there...

how about:
http://www.defender.com/product.jsp?path=-1|311|302335|7364|939818|940754&id=1620817

katana750 · May 15, 2013

vizwhiz said:

I appreciate the input. I guess one of my thoughts has been to not make this dependent on electricity (blower) and not technically below-decks, so I don't have to treat it any differently than I would a store-bought tank. I was also trying to avoid making any major mods to the main structure of the boat either. Just what I was thinking.
I hear you, Sumner, about the distance and fuel usage. Just might have to look into upgrading my thinking because of that one issue...

Click to expand

You know I was thinking of doing the same thing. I hate the gas tank rumbling around in the cock pit, and I can't tip the motor with a one gallon in the engine well. My plan... and I already bought the parts, was make a little platform above the engine for a five gallon tank then have some 45 degree angle supports back to the transom. Over top of the gas tank I was going to put a small 30 watt solar panel so the gas tank wasn't being blasted by the sun. I know the weight is up high, but right now I just sail on lakes. If the sailing gets a bit more exciting I can always move the weight down lower. The other thing I was a little iffy about was gas close to a possible spark, but I thought if I was extra careful with my connections also the chances of fumes getting to combustion levels in that spot would seem to be very slight. I always try to have my tank with a little bit of negative air pressure any way. I hate smelling gas fumes. I am interested to see what you are planing

trainmanjess · May 15, 2013

hello

i have been thinking the same thing... i have an idea about a gas tank enclosier to keep it safe, keep it out of the way, and keep is secured... i found this idea on another Mac25.... i like this idea in the picture...

sincerely
Jess

Sumner · May 16, 2013

When we bought our boat the previous owner had the tank in the laz and it was a portable so was venting in there through the cap. I didn't like that even though it must of worked for him so ...

....we moved the tank to the port side cockpit seat and tied it there. You can see it above. I'll put a cushion against it and lean back on it while Ruth does most of the work of getting us some place

. It worked fine for us and the person on the tiller can still move to that side with the long tiller handle.

Michael I'd try it there or at your feet at the back of the cockpit since that won't take any more space than an enclosure will in the same space just to get out on the water and then decide what is going to work best. I'm assuming that you are concerned about having more room for more people in the boat, but I doubt you will be taking a number of people out for the first trips.

One other option is to put a portable tank in the laz but don't open the vent on the cap (secure the tank). Then plumb in a vent line to the top of the tank and run the line to a vent on the side of the hull. Not my idea, but I've seen it done using an air hose quick disconnect on the line so that the tank can be taken out to be filled. I don't see a problem with this except that the tank might not be approved for below decks but feel the vent line would take care of that problem.

Also add ventilation....

..... either passive or with a blower like we did.....

http://purplesagetradingpost.com/sumner/macgregor2/outside-37.html

...and that isn't a hard or time consuming job.

Above is another possible solution that doesn't take up as much space. When we went out the first time we use the dinghy gas tank that you can see behind Ruth's legs.

It isn't very wide front to back so doesn't take up a lot of foot room.

Here is a link to the tank...

http://www.boatbandit.com/detail.aspx?ID=6366&Model=04156 3 Gallon&gclid=COC4qr3MmrcCFRJp7AodwxgAbA

...but we bought ours from Defender.

After that trip though we went with the portable tank on the cockpit seat that I mentioned until fitting the inboard tank.

Sum

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MrBill_FLL · May 16, 2013

I think timebandit (and others) have nice-er boxes than trainman posted.

but that's the idea.

Some others have modified the portable tanks to vent outside with long hoses tapped to the tank.

topcat0399 · May 16, 2013

I know there are alot of opinions against it but I mounted a small swim platform on the transom and it fits a 6 gal tank nicely. It has never taken a wave over it (yet) and I keep the vent closed when the engine isn't running.

I wanted it out of the cockpit and I definitely wanted it out of the Laz where the PO had it. Our laz is still open all the way to the bow. Someday I plan to put in bulkheads. It makes me feel better having the thing outside of the boat.

Roadking Larry · May 16, 2013

One of the previous owners installed a fairly large tank in the laz. Looks to be at least 10 gallons. A platform was glassed in and the tank mounted with brackets. the fill line is plumbed to the top of the back deck and the fuel line and vent are plumbed to the aft side of the motor well.

The laz is vented with two scoop vents, one facing forward, one aft with the vents "plumbed" with what looks like dryer hose to the lower part of the locker.

I will likely add a power vent.

It seems to work pretty good but I've only test ran the motor so far.

Sumner · May 16, 2013

Roadking Larry said:
One of the previous owners installed a fairly large tank in the laz. Looks to be at least 10 gallons. A platform was glassed in and the tank mounted with brackets. the fill line is plumbed to the top of the back deck and the fuel line and vent are plumbed to the aft side of the motor well.

The laz is vented with two scoop vents, one facing forward, one aft with the vents "plumbed" with what looks like dryer hose to the lower part of the locker.

I will likely add a power vent.

It seems to work pretty good but I've only test ran the motor so far.

That looks like a good setup. I think you need to have one vent...

...line to the bottom third of the locker, which we did on just the side with the blower, right arrow. I've never smelled gas so have never run the blower. I doubt you will ever smell gas either.

I went with the 19 gallon tank since it actually took up less useable space in the laz than the 12-16 gallon tanks since...

... it was narrow and long. We were happy to have it in Florida. In our other trips in the west we never used more than a couple gallons and never refilled the 5 gallon tank but in Florida if you are using the ICW to get places you will motor a lot. We might never have it filled again.

I'm in the same fix with the Endeavour and want to add a higher tank along side the quarter berth and the 50 gallon tank there again is long and thin in width and fits the area well enough vs. the ones around 30 gallons so we can still use the quarter berth for one person ( it was setup as a narrow double berth),

Sum

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MrBill_FLL · May 17, 2013

OT:
Larry how is your tank secured?

(AFAIK), USCG regs don't require a blower, only 2 passive vents.

if you want a blower, you really need to spring for the marine (no spark) blowers.

Roadking Larry · May 17, 2013

There are hold down clamps at the botom that set into molded in resesses in the fuel tank.

Fuel tank

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