19 Gallon internal Bow Fuel Tank

[Divecoz]

Though I for now........am uncomfortable with the cabin fuel tank location.. I think you guys are mixing apples and oranges about venting concerns.
I believe the Big Issue about venting is.. Carburetored Inboard Engines.. TTBOMK .. ALL built in fuel tanks are sealed below and vented to the surface.. / Deck/ Side hull / etc etc.

[grnwtrcruzn]

Thanks for the nice write up. The 90hp on my sure is a thirsty little beast so I think I'm going to have a new item to add to my mod list. cheers

[kmclemore]

Well, I'll just say this about internal tanks. Many of you know I have one on my boat - 18 gallons in the center of the aft berth - and although I do have a blower, frankly, I've never had to use it because I don't get even so much as a whiff of fuel scent in that boat, EVER. And being it's actually *in* the cabin area (not below decks) you really ought to smell it if something's at all leaking. (And don't even try to counter with the old "yes, but gas fumes sink to the bottom so you won't smell them"... I've been around gasoline long enough to know that yes, they do sink, but the stuff still stinks to high heaven when it's leaking, regardless of where those fumes are sinking to.)

If you install it properly, secure it solidly so that it's all vibration-proof (including all the hoses), and inspect it regularly (to check for cracked hoses, etc.), there's nothing inherently wrong or unsafe about having a below-decks fuel tank. As I've said before when others on this board have been critical of my choice, I'll let you know as soon as it blows up... until then, I'm right.

BTW, it's at least 8 years and counting at this point.

I have a poly 18 gallon tank installed directly beneath the aft portion of the cockpit, in the center of the aft berth. There is an enclosure around it and it is vented to the outside air. You can see it in this picture:



Fill for the tank may be seen on the cockpit sole, just aft of the pedestal.



The gas tank is made of one piece molded cross linked polyethylene and meets or exceeds industry standards (ABYC, USCG, CE and ISO):


.. and it is secured to the aft berth's sole with a metal hold-down bracket kit made for the tank.

A picture of the Perko fill & overflow vent that was used can be found here:
http://www.go2marine.com/go2_structure/ ... 729F-p.jpg

[Highlander]

I would be installing a bilge blower with that mod , I already have even without it
http://i235.photobucket.com/albums/ee20 ... 010053.jpg

http://i235.photobucket.com/albums/ee20 ... 0019-1.jpg

http://i235.photobucket.com/albums/ee20 ... 0021-1.jpg

http://i844.photobucket.com/albums/ab1/ ... 010007.jpg

http://i844.photobucket.com/albums/ab1/ ... 010010.jpg
this vent is in the head their is another one inside the V-Berth which they can be opened or closed

J

[DaveB]

I would not install this fuel tank on a MacX or M. With the weight of the tank and 18 gals fuel you are adding about 200 lbs to the bow. I already have twin 27 group house batteries aft of that location and Bow heavy with other gear.(it is maxed out)
If your group batteries and water tanks are far aft than maybe.(you also have to consider the long feed line that can chafe along the way aft)
Most long term Sailers (5 days or more ) keep there storage in Vberth and sleep aft on the Macx.
Cutting out the liner will likely cause structual problems.
Boat is bare min. structual to begin with.
Just my opion.
Dave

[aya16]

Like what was said before many older boats used to have their gas tanks under the bow, and external fill. As long as the tank is a sealed unit with gasoline hose for fill and vent as well as to the motor, It wont leak nor will fumes escape into the cabin. The tank itself, say half full will provide more floatation than it replaced, empty will be extreme floatation. Like what was said if it leaked you would know it long before it got dangerous. Some install water tanks, or holding tanks in that area, so weight shouldn't affect the boat much up front like that.

Those permanent install tanks never give off fumes, like the portable cap vented tanks most of us run. In fact I was thinking of venting my portable tanks through the hull by adding a vent line to the top of the caps, then run the lines aft, out the back of the boat, instead of venting in the cockpit. Its actually pretty easy to do.

Also some may be confused about fan venting, Like was said that's only for the engine compartment in enclosed boat motors, not the gas tanks, a carbureted boat motor gives off the fumes through the carb bowl. Not the gas tank which is already vented to the outside of the boat. No need for fans.

I would Make sure the vent outside is completely away from spray or rain, a gas tank vent is usually in the back of the boat where there is very little chance of spray going up in it. Don't use a one way check valve either, the tank vent when the boat is at rest will expel excess pressure, but when the motor is running it sucks air into the tank.
Mike

[kmclemore]

I would Make sure the vent outside is completely away from spray or rain, a gas tank vent is usually in the back of the boat where there is very little chance of spray going up in it.

Exactly, Mike. This is why I placed my fill on the cockpit sole, as well as the tank enclosure vents - they vent directly over the back of the boat, with the fumes following the lowest path.

The vents can be seen in my cockpit photo... the fill (with integrated tank vent) is the black thing just behind the helm on the sole, while one of the enclosure vents is the silver thing in the helm station (look just below the bottom-most gauge - and that's my fuel gauge, BTW) while the other is back in the motor well (hidden by the motor's head in that picture).

[aya16]

Km I take it you used that fill/ vent cap you posted the pix of? Any way when your running the engine you wont have any smell as the vents sucking, when sailing
you don't have to deal with any sloshing as we do with the portable tanks..... ohh never mind I see the vent in the ped, high and dry, thats a good set up. Has any one tried a small electric fuel pump instead of the primer bulb to prime the engine? Most all leaks will come from the primer bulb, from the cheap clamps used to attach it to the hose......Your boat is way to clean...
Mike

[kmclemore]

Yes, Mike, I did use the fill I showed the pic (and link) for. It's a Perko and works nicely. You can even step on it and it won't open. And thanks for the complements on the setup.

Re fuel pumps, I'd stay FAR away from putting in an electric pump. If that baby goes haywire (a leaking hose, busted pump seal, cracked pipe, whatever) you're gonna have raw fuel spraying everywhere and a MAJOR fire hazard on your hands. And if it does light up, it will continue spraying the stuff until you find a way to shut it off.... Yikes!

I prefer having the usual suction/siphon method to get the fuel from the tank to the motor. MUCH safer. Replacing that bulb and the hoses every few years is cheap insurance.

-Kevin

[aya16]

If I did an in line electric fuel pump, I would mount it near the motor, I would use it only to prime the motor, so I would have a switch on the ped to turn on till I hear the pump stop. Then I would turn it off and let the motor fuel pump do its thing. I would guess I would put the fuel pump in a protective case.

But in my mind I think its such a simple thing that if it was that good of an idea, it would already be on the market
Mike

[kmclemore]

Well, it would have to be a very low pressure pump, because the carbs are not designed to have a highly pressurized fuel supply... somewhere under 3 PSI I'd think.

I just don't see that the expense / space / weight / danger is worth any small potential utility.

[Boblee]

Well would certainly prefer not to have fuel inside the boat but am sure it can be done safely and looks like IMHO it has in this case as to the weight well we put 2x50l water tanks under the v berth of our and when full they are un noticeable to me and nor is the 70ah battery and tools etc near it which probably weigh more than the water.
They are probably counteracted by 80l of water under the stern bunk and two 45l fuel tanks in the lockers plus provisions as we only use the extra water on long trips but we did relocate all the positive flotation that was moved for the bow tanks and when empty they are back to basically sealed air space as I do think that is important or will be if an accident occurs re insurance/liability.

[vizwhiz]

you also have to consider the long feed line that can chafe along the way aft

To me, this is the only concern about the installation - making sure you have chafe protection at all points where the hose to the back could spend time rubbing the fiberglass hull or liner. It would not be obvious to a quick inspection because it would be between the hose and hull (or liner), so a thorough periodic inspection would be the only way to find a chafing spot.
Alternatively, you could run stainless tubing to the back, then pick up as hose again to snake your way to the engine...at least the chafing concerns would be minimized, as well as the accidental drop of a tool or the corner of a storage box.
But otherwise, MOST boats that carry fuel for real (meaning power boats) have internal tanks of some kind set up very much like this...it is not a real safety issue if installed correctly and maintained.

[Phil M]

...
But otherwise, MOST boats that carry fuel for real (meaning power boats) have internal tanks of some kind set up very much like this...it is not a real safety issue if installed correctly and maintained.

But with fuel tanks at the stern, often separate from sleeping quarters.

Phil M

[kmclemore]

...
But otherwise, MOST boats that carry fuel for real (meaning power boats) have internal tanks of some kind set up very much like this...it is not a real safety issue if installed correctly and maintained.

But with fuel tanks at the stern, often separate from sleeping quarters.
Phil M

Mine is separate - it is in a completely sealed off, separately vented full enclosure. That enclosure happens to intrude on the sleeping area in the aft sleeping area, but absolutely no air can be exchanged between it and the sleeping quarters.