Safety Question - Auxiliary fuel tank

[MercGuy]

I have an 18 foot Sea Ray bow rider with a Merc 115 outboard. I am taking a long trip this summer and I want to extend my cruising range beyond the built in 20 gallon tank.

I've purchased an auxiliary tank to mount on the rear swim platform. I would like to semi permanently mount the tank. If I do so I would like to fill the tank while it is on swim platform.

The swim platform is fiberglass, and if any gas were spilled during filling it would not get inside the boat. Sometimes I would be filling it at a gas station while on the trailer, and sometimes I would fill it while in the water at a marina.

Almost every pontoon boat I ever see has this set up.

My question is, are there any safety concerns with filling the tank while it is on the boat or should I take it off the boat first ?

Thanks !!

 

[smokeonthewater]

No issue filling it BUT it is at risk for being comtaminated with water through the vent back there.

 

[MercGuy]

Thanks, that's a good point.

Do you have any ideas for a better alternative ?

 

[smokeonthewater]

Keep it in the cockpit.

Don't spill fuel at all but IF you do the LAST place you should spill it is in the water.

 

[robert graham]

I carry a couple of 6 gallon red polyethylene jerry cans to supplement my 12 gallon main tank, but I always remove the jerry cans to fill them so not to risk electrical sparks/fires while filling....not sure it's required but seems like a good idea.....

 

[smokeonthewater]

An appliance drip pan and some absorbant pads would protect the interior also..

 

[MercGuy]

Keep it in the cockpit.

Don't spill fuel at all but IF you do the LAST place you should spill it is in the water.

Wow, I must say I'm surprised to read this. I certainly understand that we must protect the environment, etc, etc, but I would have to imagine that the single most dangerous place to keep gasoline would be inside the boat if there is a leak or a spill having explosive fumes inside the boat sounds downright dangerous.

Note that I'm taking about portable tanks. built in tanks are designed such that there is no chance of leakage inside the boat, all the venting is to the outside.

 

[MercGuy]

I carry a couple of 6 gallon red polyethylene jerry cans to supplement my 12 gallon main tank, but I always remove the jerry cans to fill them so not to risk electrical sparks/fires while filling....not sure it's required but seems like a good idea.....

This is what prompted my question. I've always heard that jerry cans should be placed on the ground when filling to avoid the chance of a static spark. I see little difference between a jerry can and the tank I pictured in my original post.

 

[NYBo]

This is what prompted my question. I've always heard that jerry cans should be placed on the ground when filling to avoid the chance of a static spark. I see little difference between a jerry can and the tank I pictured in my original post.

I believe all portable tanks are supposed to be placed on the ground when filling them. Well, at least when on land..

 

[smokeonthewater]

Open cockpit outboard engine...... No ignition source and ample ventilation.

OBVIOUSLY, if you have a major spill you should take care of it before doing anything else but the portable tank is no more likely to leak than the built in tank... Fill carefully and NOT all the way to the top... You'll be fine.

 

[robert graham]

I believe all portable tanks are supposed to be placed on the ground when filling them. Well, at least when on land..

When we fuel the plane we always run a ground wire directly to the airplane....makes a lot of sense to fill portable tanks on the ground....a gasoline fire can ruin an otherwise nice day!....I lost a brother to a gasoline fire and it leaves an impression that you won't soon forget....better safe than sorry!...

 

[airshot]

Note that I'm taking about portable tanks. built in tanks are designed such that there is no chance of leakage inside the boat, all the venting is to the outside.

If your portable tank is in good condition I see no reason why it should have more tendancy to leak than a built in tank. Look thru the rebuild section of this forum and see all the leaky old fuel tanks from built in tanks people have to remove. I have no fears using a good condition portable tanks in my boat.....proper caution must be used at all times as with any fuel source!!

 

[Frank Acampora]

ALWAYS remove a portable tank and fill it on the concrete or the dock. The plastic of the tank can build a static charge that will not be drained off by the boat hull. If you absolutely MUST fill it on the boat run a ground wire using alligator clips.

 

[MercGuy]

ALWAYS remove a portable tank and fill it on the concrete or the dock. The plastic of the tank can build a static charge that will not be drained off by the boat hull. If you absolutely MUST fill it on the boat run a ground wire using alligator clips.

^^^^ This

I did some more research and found many reputable sources that insist that portable tanks should be removed and placed on the ground or dock when refilling. I also read that it is good practice to touch the fuel pump nozzle to the back side of the portable tank (away from the filler) BEFORE opening the tank to discharge any potential spark before opening the tank.

I will remove my tank before I fill it.

Thanks to all for your input !!

 

[MercGuy]

If your portable tank is in good condition I see no reason why it should have more tendancy to leak than a built in tank. Look thru the rebuild section of this forum and see all the leaky old fuel tanks from built in tanks people have to remove. I have no fears using a good condition portable tanks in my boat.....proper caution must be used at all times as with any fuel source!!

On my boat there is a significant difference. My built in tank has 2 stout fillers on the top side of the tank with sturdy hoses attached by 2 stainless steel hose clamps at each end of the line. The lines are vented to the outside which means that there can never be a build up of pressure in the tank. A leak could only happen if there was a complete break in either a line or the tank itself.

A portable tank (especially the new EPA compliant tanks) are not vented and develop internal pressures. On most tanks the caps are relatively flimsy plastic which are prone to leak, especially due to the internal pressure created when the gas expands.

Read some of the reviews of tanks on Amazon and you will read about a lot of leaking portable tanks

 

[smokeonthewater]

In that case the problem isn't the portable tank but rather the defective tank....

My 1956 omc tank wasn't vented and never leaked a drop.... In fact there was no fuel pump on the motor... Instead crankcase pressure was run to the tank an fuel was pushed back to the engine by pressure in the tank...

I still have several steel tanks from the 70's and 80 and they don't leak either.... If the new tanks are such junk maybe you need to get on ebay and pick up some old tanks.

 

[airshot]

When plastic tanks first came into play there were many manufacturers making them, industry standards were lax in the beginning. Many of these poor quality tanks still show up from time to time. When the auto industry became involved with plastic tanks the standards for fuel tanks vastly improved to the point where plastic tanks had to withstand a greater impact and seam split test than any metal tank. In recent years we have been importing many cheap copies of plastic tanks that are very inferior and not required to pass our own standards. Top quality mfgs making tanks in the USA are required to meet these standards where imports have to meet their own country standards and we know how good those can be, these are the tanks you see having issues. Buy a quality tank and you will be fine but get an economy tank and......it may not be pleasant. As a Toolmaker for more than 45 yrs I was involved in the introduction and testing of plastic fuel tanks from their inception. Today I have no issues with a good quality plastic tank, been using them for years without issue, but I do stay away from cheap imports as I value my family and my boats to take chances on cheap products.