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My little diesel is shot on my Ericson. I hung a 6 hp, 2 stroke off the back. I have an existing 10-12 gallon internal metal fuel tank for the diesel. I would like to clean that out and rig the tank for use with gasoline to feed the outboard. I know I've got to make sure venting is okay and existing tank in good shape, but assuming that is alright, aren't I in the same position as anyone using a gas auxiliary with an internal tank. Can I make this work okay? Thank you. Greg
 

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Sure, go for it.
Always filter the gas to the outboard. I suggest a
Racor system, same as for Mercruiser.
For the first tank mix, the oil/gas ratio at 55 to 1,
instead of 50 to 1. If the outboard smokes too much,
you will have to clean the sludge out of the bottom of the tank.
It will leach into the gas mix with time, and raise the octane level.
 

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If you do this you have to make sure all equipment in the compartment is explosive proof, the compartment will have to be sealed off from the rest of the boat and you will have to add ventilation. You will also have to change the fill plate to read gasoline. Check USCG regs on this one but I am guessing it will be a fair amount of effort. Gasoline is nothing to fool around with if you have ever seen a boat blow up from a gas leak you would understand. I have seen it and it is not pretty.
 

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Dont forget to add a 'flame arrestor screen' on the vent outlet of your tank .... just a finely woven stainless steel screen between the hull/transom and the clamshell, etc. that protects the vent opening.
Such prevents gas tanks from going *boom* if there are any 'sparks', etc. near the vent opening ... and is required by ABYC and your insurance carrier.

You'll also need to add a USCG approved ignition-proof 'bilge blower' and non-flammable ducting ..... to be run for several minutes to evacuate any heavier than air gasoline fumes from the bilge and other 'low' spaces.
 

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You'll also need to add a USCG approved ignition-proof 'bilge blower' and non-flammable ducting ..... to be run for several minutes to evacuate any heavier than air gasoline fumes from the bilge and other 'low' spaces.
Rich, hang on there a sec.. the OP's got an outboard. It's only the tank that's in the boat. ;)

My advice would be to plumb the tank vent into the cockpit so that any flammable vapours don't get into the bilge whilst he's filling the tank- but other than that, as Sony2000 points out,he should be good to go.
 

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Rich, hang on there a sec.. the OP's got an outboard. It's only the tank that's in the boat. ;)

My advice would be to plumb the tank vent into the cockpit so that any flammable vapours don't get into the bilge whilst he's filling the tank- but other than that, as Sony2000 points out,he should be good to go.
Well you are still going to have vent the compartment so it makes sense to treat it like a regular inboard install. There are lots of things that can trigger an explosion like a battery charger or any kind of switch. And the blower would make it so you could vent out any leaks. I would think any insurance company would require it anyway.

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Rich, hang on there a sec.. the OP's got an outboard. It's only the tank that's in the boat. ;)

My advice would be to plumb the tank vent into the cockpit so that any flammable vapours don't get into the bilge whilst he's filling the tank- but other than that, as Sony2000 points out,he should be good to go.
I perceive that the OEM diesel tank is INSIDE the boat ... and would be required to follow the same USCG regs as any 'inboard' fuel installation. ;-)
 

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Discussion Starter · #8 ·
Right. OEM diesel tank is inside boat and rigged properly for whatever requirements for such a tank - and insured. I will check everything, though, as I've never analyzed it that carefully when running the diesel. Thank you everyone for your responses.
 

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I perceive that the OEM diesel tank is INSIDE the boat ... and would be required to follow the same USCG regs as any 'inboard' fuel installation. ;-)
What are the regulations for an inboard gas tank, assuming it's feeding an outboard engine? It seems like if the fill and the vent are on the outside of the boat you shouldn't need any special blowers inside.

But I guess regulations don't always make sense...

What if a gasoline tank is in a vented locker, like a propane tank? Would that be OK?
 

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This boils down to safety and common sense as much as regulations. Yes if the tank was in a locker like propane it would be ok. Gasoline vapors are heavier than air and will flow to the low point. Imagine the dry ice fog you always see in science shows it flows slowly down. If you have a small leak the vapors will flow down so you want to vent those fumes over board a blower being the surest way to do this. you also do not want anything that can spark in the compartment. Some mentioned venting into the cockpit this is not a good idea for the above reasons. All in all I would think the PO would be better off with a portable tank outside. Gasoline can be dangerous you need to use care with it in confined spaces.
 

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Many of the rules regarding venting and explosion proof fittings are the same on dry land (NFPA 30, IBC). As part of my work as a tank inspector, I've investigated explosions caused by everything from a grinding spark reaching a mis-locateded vent on a used oil tank (it was brought down the grade level from the tank top,m and though the oil was not ignitable, the lighter material that condensed in the vent line was) to the static spark off a man's feet on a dry day. Placing everything in a boat hull only makes the details more important.

I would add that the tanks should certainly be inspected. Remember, the CG does not regulate diesel tanks, and thus the installation may not meet any standard.
* It may be corroded or too poorly built for gasoline.
* The fill hose is probably not suitable for e-10 gasoline. If it seeps the bilge could fill with gasoline while you're away.... Hence the need for ventilation or a separate compartment.
* The vent may be too small.
* The fuel lines are probably unsuitable.
* The gasket on the sending unit may be unsuitable.

None of these precautions are over stated, either by code or common sense.

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This may be a smart conversion, but there is much to go over. Read the standard and review with a person knowledgeable on gasoline tank installs. If I could not manage a separate vented compartment (I've had 2 boats with these--also handy for extra small propane cylinders), I would use an on-deck tank.
 
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