Outboard Style Fuel Tank

[GorgeSantana]

I'm interested in hearing the downside to using an outboard style fuel tank instead of my 40 year old original tank. Here is my situation:

I have a 40 year old tank that's been missing the o-ring for at least three years (I just bought it and have little prior history).

I've already pumped out green water and lots of nasty varnish and sediment. I believe the tank needs to be boiled, etc. to be truly problem free.

The pickup tube is currently clogged.

I would need to pull the engine to remove the tank. I have no other reason as of now to pull the engine.

I sail on the Columbia River, mostly within 20 miles of my slip. I use the engine mostly for in and out of the marina. There are some trips that would involve an hour or two of motoring.

I have a ventilated compartment in the rear of the boat. It has a large lid for direct access from above. There is a 4 inch vent with a scoop in it.

I'm thinking of using an outboard tank resting in the ventilated compartment. If I used a 6 gallon tank and a couple 2 gallon reserve tanks, I'd have 10-15 hours of motoring time. I could use the 2 gallons as easy to carry refill tanks (we have limited refill at the dock).

I could plumb the vent from the outboard tank directly to the outside if needed. Or just open it during use and close it afterwards.

It seems the danger to gas on boats is leakage from the tank and buildup of fumes. Simple strapping would keep the tank from rubbing and developing a leak. The venting seems easier and more reliable than the original tank down in the engine compartment.

Am I missing something here or overlooking a safety issue? Would this violate a coast guard regulation?

thanks,

mark

[Chip Hindes]

Oubboard tanks are not vented because they are meant to be used above deck. They have a vent in the filler cap which is meant to be closed except when the motor is running. If you open the vent when the tank is below deck it will vent into the bilge. If you leave the cap vent closed you'll eventually starve the motor of fuel; with a "real" fuel pump (as opposed to an outboard fuel pump) you might actually be able to implode the tank.

I'm pretty sure using an unvented outboard tank below decks is a violation of Coast Guard regs. As with most Coast Guard regs, they are not chosen at random but are meant to protect you because it is just plain dangerous to do otherwise.

My boat had exactly the problem you are describing when the previous owner had it. the low cost solution was the marina installed a small permanent tank in the lazarrette. They built a small platform out of marine plywood and PT lumber; it was hooked to the original filler, vented to the original vent, grounded and even hooked up to the fuel gauge. The only thing they neglected to do was tie it down properly, but I could have done that if I'd wanted to. I had the motor out of my boat for rebuild this summer and took the opportunity to replace the original steel tank with a new, larger Moeller. I pulled the small tank out of the lazarrette but I still have it. Let me know by PM if you're interested and I'll give you the particulars.

[Don Moyer]

Mark,

While others are preparing to weigh in on this interesting subject, our very first boat (our beloved "Water Music") had factory-installed mounting pads for two outboard tanks in the lazarette which we used for the 12 years we owned the boat ("Water Music" was originally an outboard-powered boat). I was always very happy with the convenience of this arrangement for at least the following reasons:

1) Ease of cleaning/servicing.

2) The economy of replacing, as we eventually did after ten years or so.

3) Ease of refueling in cases where we didn't have access to a fuel dock; e.g. transporting the tanks to shore in our dinghy and filling them up at a local gas station.

Don

[GorgeSantana]

My Plan

Thanks for the information and advice. I'm convinced this old tank has to come out to be cleaned at some point. And today is not that day.

For $129 I can buy a 14 gallon Moeller Below Deck Tank from Amazon. I'll put this in the aft lazarrette and plumb the vent to the outside. I can easily plumb to the Racor from there. I may even hook up the gas gauge it comes with!

I may be spending $100 more than I need to (below deck tank vs above deck) but I've spent more and gotten less.

Any thoughts on the fill tube? Is it a significant safety issue to have it down in the lazarrette vs plumbing it to a deck plate?

Mark Dane