outboard motor gas tanks?

local marine dealer told me that all the new gas tanks have a cap that functions similar to the ones on all the gas jugs that everyone hates, and that don't work well. seems theyre meant to let air in, to allow gas flow, but dont let any air out. I have one of these, and the tank will blow up like a basketball with the vent screwed all the way open. ive heard these can malfunction, and restrict the gas flow to the engine, and allow moisture to get into the tank. does anyone have any experience with these, or knowledge of them? thanks.

mine does the same thing

buy a different cap that has a manual screw vent and just leave it open. I have one of the newer plastic tanks and bought a cap that's for the old snapper rear engine rider lawn mowers, fits perfect. But I still use the old metal tanks cause I like them better

They are junk , some Obama EPA good for the environment junk. Scan yard sales flea markets for an older good one and retrofit the connectors to your engines hook up.

I bought some of those gas can vents that are plastic and flip open to vent a gas jug, they do work good on the boat cans you are talking about. 2nd on the metal boat cans, they are way better

One thing about those new tanks caps is that you have to disconnect the hose from the outboard when you leave the boat or that pressure can bugger up the membranes in the fuel pump.
It does not happen all that often , but I have fixed a fair few due to that issue.

I have some rental Merc motors, The tanks were blowing up like balloons in the hot weather, my dealer showed me how to take a small screw driver and pry the rubber bladder out from the underside of the cap, problem fixed. Simple to do takes less than a minute.

Metal cans are also a lot safer ! The plastic container can generate static and cause a fire. I know because I burned down a building from that very cause !

I had a plastic boat tank swell up so round it rolled right off the back of the pontoon and was dragging it by the gas line. Another cracked and leaked, I think it swelled during the day and contracted at night, finally wearing a crack in it. Government safety rules I suppose. I restored a couple old metal tanks. I recoated the insides with "Tank Renew" repainted the outsides with rustolem red. No more problems.

My outboard tank wouldnt vent the best, so i took a drill bit to the vent hole and opened it up a little. It had a little set screw that you open and close. I took it out and reamed the under side. Vents both ways like a champ now.

gone trappin......this cap has a manual vent screw, but only vents one way.

scuba,,,,ive heard that too,,another potential problem I'm trying to avoid.

mskrtman,,,,is this a rubber o-ring that forms a seal between tank and cap, or something else.

the plastic tank I have fits perfectly in the transom well, so id like to keep that, rather than a steel tank.

ive heard that old style caps are available online, to bypass this regulation. does anyone have any experience with these?

thanks to all for the help so far.

also,,,has anyone had issues with these caps letting moisture into the tank?

TTT........