fuel tank size/placement

[mikemerrill50]

I'm trying to figure out how my fuel system will be done on my bowrider. my boat has 5 stringers, and there is no room for a below-deck fuel tank. I have been told to account for 10% of your engine's hp in gph (15 gph for a 150hp motor). if i go with a 150 hp motor, i would want at least a 30 gallon tank. however, it would be hard to fit a 30 gal. in the rear of the boat under the rear seats near the bilge. also, i would want to be able to clean the bilge pump without removing the fuel tank. i am also worried about all that weight at the rear of the boat along with the motor, as i imagine this would cause serious weight imbalance and trim problems. what would you guys recommend? should i go with a multiple tank setup? if i do, i imagine i would need to get multiple fuel gauges, and that would get expensive and ugly. what have you guys done?<br /><br />thanks!

 

[Reel Poor]

Re: fuel tank size/placement

Since your doing the stringers in the boat why dont you custom build an area into the stringer system to accept a under the floor permenant fuel tank. It would be fairly simple to install around 40 or so gallon under the floor.

 

[mikemerrill50]

Re: fuel tank size/placement

i was considering doing that, but most people have said not to change the stringer design of the boat, so I would prefer not to. if yall think i can still do it, then i will. anybody else?

 

[Buttanic]

Re: fuel tank size/placement

You could have a tank custom built to fit in the avaible space between the stringers. Probably won't be as cheap as an off the shelf tank but might solve your problem.

 

[Mark42]

Re: fuel tank size/placement

Look into saddle type tanks that go under the gunnel. <br /><br />Take this link to Tempo marine products, pick out the size tank you want, then call iboats and get a price on the tank. You should be able to get a pair of 18 or 25 gallon tanks that will work for you without changing the strigner design. They are about 8" wide at top, and only 5 or 6 inches thick at the bottom, so the tapered design fits the sides of the boat nice. <br /><br /> Tempo Gas Tanks.<br /><br />Plus you have the option of designing in the tanks before choosing the seating and side storage. It would be nice to get the tanks 1/3 or 1/2 the way up the boat from the rear for balance. Remember a pair of 25 gallon tanks will weigh about 400lbs when full of gas. So you want to position them in a neutral location so the weight does not have negative affect on handling. <br /><br />If you are going to add permenant tanks, I suggest going with the larget you can fit. Just because the boat can swallow 50 gallons of fuel doesn't mean you have to fill it. And the extra capacity will come in handy sometime.

 

[E. E.]

Re: fuel tank size/placement

One option for you is to do something like this. You mentioned that you did not want to alter the stringers but if you replace them, you could do as I did to accomodate a 31 gallon in floor tank that was never there before.

 

[E. E.]

Re: fuel tank size/placement

Forgot to add link http://i45.photobucket.com/albums/f87/1967skibarge/a9d2eadb.jpg

 

[mikemerrill50]

Re: fuel tank size/placement

thanks for all the help, guys! i'm thinking of going with the dual tank setup mark42 mentioned. however, i've been looking for tee fittings online, and i can't find them for fuel lines. i assume this is what i would need to do. run a fuel line out of each tank to the rear into a tee fitting, combined the lines into one fuel line, going to the primer, fuel filter, etc., then into the engine. i would like the tanks to be used almost equally, so the weight balance is maintained. if i do this, then i should also be able to just have one deck fill, becuase as i fill one, if they are connected by one hose, they will both rise at the same rate. also, I would technically only need one fuel gauge (but i would probably have two). sound right?

 

[Always Broke]

Re: fuel tank size/placement

Something else you might want to consider is having the tanks custom built at a local welding fabrication shop around you like buttanic mentioned. Tanks under the floor give you a lower center of gravity and won’t throw your weight off from side to side when one gets low. I have a friend who runs such a shop and people come in with blue prints on how they want their tanks built so they end up with what they want. If you go that route draw up your plans including fuel fill, vent, gauge placement, and sizes and also bottom angle, dimensions etc… I would include a few baffles in the tank so when your trying to get over the hump all the gas don’t go to the rear of the tank. Take em into a shop that does aluminum work and see what he has to say. If it’s a simple design you might be surprised at the price compared to buying two tanks. You’ll have to be the judge of the pros and cons. As far as the gauges go, I have a bass boat with duel tanks and one gauge. There’s a three way rocker switch that shows how much fuel is in each tank just using one gauge. Here’s a link to a brass three way valve for $21.00<br /> https://www.surplusunlimited.com/Merchant2/merchant.mvc? If you decide to go with two tanks.

 

[tashasdaddy]

Re: fuel tank size/placement

mike imho, you need a tee valve, that will stop all gas flow, right tank, left tank, both tanks. you need 2 guages,2 vents, two fill tubes. the reason being is when you are filling you don't want to wait for the equalization between tank connected with a 3/8" hose. just turn the valve to off, and fill boths tanks. then set the valve where you want it.

 

[Mark42]

Re: fuel tank size/placement

You want this 3 way valve. There is a cheaper one, but it doesn't have detents.<br /><br />

<br /><br />And a switch to flip between the two different fuel senders on the tanks, or just use two guages.<br /><br />Check out my fuel tank project, I added one permanent tank to the bow, but a lot of the hardware is going to be the same.<br /> 65 MFG Fuel Tank <br /><br />You must use marine grade fuel line to meet regulations. Copper is also allowed, but I went with rubber because it was easier to work with. Do not use any automotive fuel line, or radiator hoses for filler necks. Big no-no. Use stainless clamps made for fuel neck to be sure you meet regs. And another thing, all fittings and valves must be above the top of the tank. Don't mount the 3 way valve on the floor. If it starts leaking, it can siphon both tanks into the boat! Just a good idea to run all fuel lines above the tanks or as high as possable in case of leaks.

 

[Reel Poor]

Re: fuel tank size/placement

Its also against CG regulations to connect fuel tanks together with rubber hose. By this I mean a rubber hose that will be used to equalize fuel level.<br /><br />A shut off valve is also a necessary componant when using dual tanks. If one of the tanks runs empty the pump will suck air from that tank instead of fuel from the other.<br /><br />Ever tried to drink from a straw with a hole in the side of it?

 

[mikemerrill50]

Re: fuel tank size/placement

so what i will probably do is have two tanks, one under each gunnel. i will have a fuel nozzle on each side, a fuel pickup hose and a vent hose on each side, and the hose running to the engine will go to the valve mentioned above. i will run the fuel lines on the underside of the gunnel, and they will meet behind the rear seats to one side so that they are still higher (or same height) as the connectors on the tanks. i will have a sender in each tank (tempo includes them), and i will either have a switch or dual gauges (which is what i'm thinking i'll do)<br /><br />i thought about the custom aluminum tank, but i've heard too many horror stories about aluminum tanks rusting. also, i would like to have tanks made specifically for marine purposes.<br /><br />reel poor, you mentioned having a shutoff valve for each tank. the valve mentioned above will serve that same function, i would assume. are you saying i should have an additional shutoff valve for each tank?<br /><br />thanks, guys.

 

[Mark42]

Re: fuel tank size/placement

Originally posted by mikemerrill50:<br /> ...and i will either have a switch or dual gauges (which is what i'm thinking i'll do)...<br />

Dual guages would be cool especially if the dash has the space for them. Gas guages are inexpensive, and it's nice to know how much gas you have total at a glance. <br /><br />And don't forget to pick up a water separating fuel filter like a Racor model with the blue see through bowl and drain. Will save you mega headaches if you ever get a load of water laden fuel or water contamination.

 

[Reel Poor]

Re: fuel tank size/placement

Originally posted by mikemerrill50:<br /> <br /><br />reel poor, you mentioned having a shutoff valve for each tank. the valve mentioned above will serve that same function, i would assume. <br />thanks, guys.

Sorry for the confusion.<br /><br />You are correct. The control valve in the pic is sufficient.

 

[mikemerrill50]

Re: fuel tank size/placement

with that water separater, should i get one for each tank, or just one main one in the line going to the engine? i am completely redoing my dash... i'm cutting it out and fiberglassing in a new one (i work on cars, so this is one thing i'm actually good at!). they will be recessed gauges (recessed about 3/8" back), and will have some sort of vinyl or mirror around them. <br /><br />thanks, guys!

 

[mikemerrill50]

Re: fuel tank size/placement

reel poor, would it serve any additional purpose? since they aren't expensive, i just want to make sure it wouldn't hurt to have them on there. if it would be completely pointless, then i won't.

 

[Mark42]

Re: fuel tank size/placement

Originally posted by mikemerrill50:<br /> with that water separater, should i get one for each tank, or just one main one in the line going to the engine? <br />thanks, guys!

I think one in the common line to the outboard will do it.

 

[Reel Poor]

Re: fuel tank size/placement

There is no real need for the second valve. Run hoses from tanks to valve, then to filter, then to engine.

 

[mikemerrill50]

Re: fuel tank size/placement

i am thinking now that I am going to make my own tank. it would be considerably cheaper, and i can easily do it with fiberglass. i recently got a book on boat fiberglass, and it had a quick part mentioning how well a fiberglass gas tank lasts and holds up. I can easily make one with fittings ordered from different online places and a universal electronic fuel sensor. however, will i be violating uscg regulations? i have heard uscg regs only apply to retail fuel tanks, not homemade ones. any input?