trailering with unvented gas tank

[Swivelhart]

My glastron came with two 6 gallon metal OMC tanks. They do not have a vent screw on them so my question is how do these vent the gas when trailering down the road while the gas sloshes around inside. I would hate to arrive at my destination to find gas leaking all over the place in the bilge area. Also if they are designed to expand what happens when I plug the fuel connector on the engine. Is it going to spray gas all over from the pressure or do I leave it connected at the engine. If I leave it connected at the engine doesnt all the pressure push fuel into the carbs or put a lot of pressure on the needle valves. Sorry for the lengthy question I just want to be sure of every angle. I cant afford a big plastic vented tank right now cuz im leaving in a few days for camping. Thanks for any input!

 

[Philster]

Re: trailering with unvented gas tank

The top of the large cap is the vent. Pressure forces it open. "Open" is being kind, as it won't visibly open.

.(Fumes squeeze past/out the top of the cap)

.

 

[nlain]

Re: trailering with unvented gas tank

That tank has to be vented, you would not get the gas out for very long if it was not vented. Also when the tank sets in the hot sun in your boat it would expand and change the shape permanently.

 

[Swivelhart]

Re: trailering with unvented gas tank

Thanks for the piece of mind. I figured there had to be some kind of arrangement. Gas fumes have been around longer than OMC tanks.

 

[Philster]

Re: trailering with unvented gas tank

I never liked those OMC metal cans. Never liked the venting arrangement.....

.

 

[Home Cookin']

Re: trailering with unvented gas tank

I always assumed (and was told) to leave the cap loose to vent, and tighten only intransport to keep it from spilling. Being steel you don't have the expansion/contraction issue. I recall opening a tight cap to a lot of pressure. Been a while, though.

 

[JimS123]

Re: trailering with unvented gas tank

Those were the best tanks ever invented. Self-venting, so you don't have to worry ever. I replaced one with a new plastic tank when I bought a new boat and ended up throwing it away and just repainting the old OMC tank. Its a shame they don't make them any more.

With a manually vented tank you're damned if you do and damned if you don't. Leave the vent open and it sloshes around and drips if the tank is full. Close it for transporting and the tank implodes or explodes. Leave the cap loose and forget and you have a mess.

Moot point now anyway. As of 01/01/2011 all manually vented tanks are outlawed. However the law was worded funny. Can't use a manual vent on a motor mfg after the date. But you can still buy a manual tank if you have an older motor. Rumor is that the manual tanks are on the short list. Just look at current motor manufacturer's sites - they have all discontinued sale of 6 gal tanks. Now only after market available.

 

[V153]

Re: trailering with unvented gas tank

I was always told those style tanks had some sort of venting feature incorporated into the hose connection?

 

[scipper77]

Re: trailering with unvented gas tank

my tank looks exactly like that and the cap has three positions, Loose, tight, and off. I just leave the cap loose. Of course I never fill past 2/3 of a tank. My little 5.5 hp motor couldn't go through 1/2 a tank in a day if I tried. 6 gallons lasts me close to a whole season.

 

[sw33ttooth]

Re: trailering with unvented gas tank

^ "scipper77" said it right i dont know how many times i've filled my little gas tanks 100's! after you fill the tank put the cap on turn it all the way tight then back it off slightly you may hear a hiss from preasure. the cap shouldnt come off but it will have play in it back and furth.

 

[scipper77]

Re: trailering with unvented gas tank

my tank looks exactly like that and the cap has three positions, Loose, tight, and off. I just leave the cap loose. Of course I never fill past 2/3 of a tank. My little 5.5 hp motor couldn't go through 1/2 a tank in a day if I tried. 6 gallons lasts me close to a whole season.

^ "scipper77" said it right i dont know how many times i've filled my little gas tanks 100's! after you fill the tank put the cap on turn it all the way tight then back it off slightly you may hear a hiss from preasure. the cap shouldnt come off but it will have play in it back and furth.

Just to be clear, my tank cap actually locks into a position where the cap is loose but will not rotate. There are three positions. I did not mean that I loosen it to a point I feel comfortable with, I meant there is a position built in to the cap for keeping the tank sealed, rotate a bit and the next position the cap is loose but you can not remove it. Rotate it to the next position and it will remove the cap.

 

[JimS123]

Re: trailering with unvented gas tank

Just to be clear, my tank cap actually locks into a position where the cap is loose but will not rotate. There are three positions. I did not mean that I loosen it to a point I feel comfortable with, I meant there is a position built in to the cap for keeping the tank sealed, rotate a bit and the next position the cap is loose but you can not remove it. Rotate it to the next position and it will remove the cap.

That's exactly how the OMC tank caps are supposed to work. Keep her turned all the way clockwise and it'll be just fine.

The middle position is to release any pressure without having the cap fly off. Then turn CCW to take it off for a refill.

Instead of doing what somebody said on the internet or what you were always told, just read the owner's manual. They started making that exact tank in about 1957 and its worked fine all these years. I have a 1964 and a 1984 model and they both seal just fine. Only the older of the 2 has ever been serviced, and that was to replace the guage float due to ethanol.

 

[109jb]

Re: trailering with unvented gas tank

On that tank, when hooked up to a proper OMC fuel hose running to the engine the tank is vented through the connector/hose. If it isn't hooked up to the fuel line it is not vented and will build pressure on a hot day. The twist cap has 3 positions:

All the way CCW - obviously for removing the cap
All the way CW - for a tight seal
In-between - to relieve internal pressure when removing the cap

I ran that same tank on my Starcraft for many years. I had 4 tanks I used in that particular boat for extended fishing trips. 2 just like the one in the OP's picture, and 2 plastic. The plastic tanks had no provision to use the OMC vent arrangement and you had to vent the twist cap or the tank would collapse and engine would die eventually. With the metal tanks, just hook up the hose and run without loosening the cap or anything. Worked perfectly for me for many years. I much preferred the metal tanks over the plastic ones.

 

[V153]

Re: trailering with unvented gas tank

On that tank, when hooked up to a proper OMC fuel hose running to the engine the tank is vented through the connector/hose

Thank you! Pair of lil spring loaded needle valves if I'm not mistaken?