new style portable fuel tanks

J

jack keifer

New member
We have 4 portable fuel tanks for our Honda 50 EFI. 3 old style with the fuel gauge and vent in the cap, and sad to say, a new style 6 gallon with the separate gauge and what appears to be a non functioning vent in the cap. We only use it on longer trips. Recently when under way at about 4500 rpm, the engine rpm started dropping. After slowing and checking several items and increasing speed to 4500, the engine ran fine for a period of time. After we had the boat loaded on the trailer, I loosened the filler cap and heard a significant hiss. Obviously air rushed in to cancel the vacuum in the tank. Our dealer says he can no longer get the old style tanks. So has anyone drilled either the filler cap or the tank to provide an adequate amount of ventilation? If so where and how did you manage the cuttings to keep them out of the tank? Also did you add any kind of sponge to the hole to keep any dirt out of the tank?
Thanks
Jack
 
In 2011 the EPA/CARB compliant outboard tank caps eliminated the old "open" knob vent. They have a vacuum vent--which should open under vacuum, and in case of excessive pressure in the tank. I suspect that your "flapper" valve is stuck--or defective. I would try and take it apart first. Drilling a hole where it is open all of the time is probably not the best plan.

I know you can still buy the old style caps (as you can buy new style caps) (but of course I would not suggest that you use an old style cap in violation of EPA……)

A piece of foam etc, could cause issues--best to get the cap you have working properly--or get an old cap...
 
You live in Idaho and you can do probably do whatever you want without worrying about the EPA. With that said, I don't think you should drill it out for numerous reasons. I read somewhere the old caps do not fit the new tanks....It might have been here....LOL....There are some old style tanks available at amazon.com I think. You could always buy an old OMC steel tank and adapt it to your honda. There are normally a number of them for sale used that are just fine.
 
I may have solved the problem. I won't know until I run the boat again with this tank which could be a while. First it is true that an old cap will not fit on a new tank as the filler openings are different sizes. The vent in the cap is under a threaded plastic screw which has an o-ring in a groove at the bottom. Then under the screw is a soft rubber nipple that is attached to the cap. It appears that when the screw is opened all the way that the vacuum produced by the fuel consumption should pull the rubber nipple open and allow air to replace the displaced fuel. The nipple on this tank was stuck to itself and so no air would pass to the tank, so I opened it in such a way that it will always allow air to enter the tank. No drilling required. We will see if this solved it.
 
I may have solved the problem. I won't know until I run the boat again with this tank which could be a while. First it is true that an old cap will not fit on a new tank as the filler openings are different sizes. The vent in the cap is under a threaded plastic screw which has an o-ring in a groove at the bottom. Then under the screw is a soft rubber nipple that is attached to the cap. It appears that when the screw is opened all the way that the vacuum produced by the fuel consumption should pull the rubber nipple open and allow air to replace the displaced fuel. The nipple on this tank was stuck to itself and so no air would pass to the tank, so I opened it in such a way that it will always allow air to enter the tank. No drilling required. We will see if this solved it.
 
If it were me, I might be inclined to write my Senator to tell them that the EPA's regulations are causing life safety issues on recreational boats. But, that's just me...
 
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