fuel tank

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tasthree
Posts: 34
Joined: 29 Oct 2017, 20:54

fuel tank

Post by tasthree » 07 Oct 2019, 14:15

Fuel tank questions I couldn't find answers to in a search. I have a Bluskies 3 gal tank I got with a motor I bought for my last boat. I have a different boat with a new Yamaha motor now. I started off using that Bluskies tank. The tank has a vented cap and the plastic seems pretty thick as you can barely see thru it for the fuel level. I had no gas fume smell issue. It’s just to small sometimes for larger lakes or if we troll all day with the gas motor. So I switched over to a old 6 gal made in USA Attwood tank our newer boat came with. The boat is a 84 and I don’t know if the tank is that old. It has a vented cap and you can see the fuel level in it pretty good. Instead of red it’s an orange color on the top of it from being faded. It also hadn’t been used for years. After using it for a couple of months I started to get a constant gas smell. Just enough to bother/concern the wife. There are no leaks or such in it. I removed the fuel from it and let it sit for a couple of days with the cap off. Then I put the cap on and closed the vent and let it sit for a little bit more. It still reeked like as if the plastic was permeated completely thru with gas. I don’t ever remembering having this issue with a plastic gas tank or can. Out of curiosity can an old plastic tank get permeated and constantly reek of gas? I’m setting that tank aside as a backup and need one to replace it. I’m considering a new Yamaha 6 gal tank for about $107 including shipping. Any comments on the quality of the Yamaha plastic tanks? It probable has no vent which I’m not a fan of the non vented tanks and always worrying about them bloating up. I know about the FDV’s just don’t want to have to install one. Also realize I could just crack the cap but I’m afraid I’ll forget and slosh fuel everywhere when trailering or such. I’m also considering an older metal tank. I have never owned a metal outboard tank. Do these have a baffled vent in the cap or are they half turn for vent position? Do you have to worry about fuel sloshing out of the vent in rough water or while trailering down a rough gravel road with a metal tanks vent? I found a made in Japan Yamaha metal tank that looks to be in very good condition on the outside. It’s a little pricey at $120 plus $24 shipping. Not being able to look at the tank before purchase I would have concern of rust being in it or developing on the inside. Even though my new motor has a fuel filter I would have concern with small rust particles getting thru to the fuel injection system. My new motor is a four stroke Yamaha F25. I use non ethanol 87 octane gas with fuel conditioners added. Thanks.

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1960 yellowboat
Posts: 199
Joined: 24 Apr 2019, 08:04
Location: Homosassa Florida

fuel tank

Post by 1960 yellowboat » 10 Oct 2019, 11:42

All the new EPA mandated gas tanks no longer have a vent to the outside air. Regardless of brand. In the hot summer sun, they cause the fuel vapor to expand and the tank "blows up like a balloon" Inside the tank, pressure builds up and fuel is forced out the line fittings and into the engine. You may still be able to buy a replacement manually vented cap for the new tanks for around $15.
Or do what I did.
Find an old fashioned STEEL tank for cheap and rebuild it. They don't leak. They don't swell.
Here's one I fixed up.
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DaleH
Donor
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Joined: 12 Dec 2014, 14:32
Location: Eastern Mass

fuel tank

Post by DaleH » 10 Oct 2019, 12:45

If plastic, find an older Mercury tank with built-in handle going across the top, is made of really thick plastic.
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red91sit
Posts: 16
Joined: 06 Oct 2019, 06:30

fuel tank

Post by red91sit » 14 Oct 2019, 20:58

These new plastic tanks seem to be of questionable quality. My lawnmower 5 gallon jug started sweating through the front of the jug, no pin holes, it was leaking straight through the plastic. That was a new one, I wouldn't be shocked if a sun baked one has similar issues.

turbotodd
Posts: 1167
Joined: 24 Dec 2011, 22:06
Location: 72032

fuel tank

Post by turbotodd » 14 Oct 2019, 22:10

A good EPA tank will vent when pressure exceeds I think 6 psi? I can't remember...but we had to test a slew of them a while back as part of a recall.

A junk (mass market) tank will swell up like a toad at 3 psi, and I've had one split at the seam-stranding me in the middle of the lake (not even mentioning that the bottom of the boat was FULL of gasoline and the floatation that came into contact with it was destroyed). Thank goodness for a breeze that helped blow me toward the ramp and I'm sure glad that I don't smoke. That was an Attwood tank as I recall.

On a new EFI motor, you're not gonna fill the motor up no matter how much pressure you put on the line, period. You'll blow the primer bulb up before you get a single drop of fuel into the engine, and at that point you're likely to also destroy the separator (on the motor) and perhaps the fuel lines under the cowling. There IS a float, needle & seat in the VST but you're still not going to get any fuel into the engine even if you overpressurize the needle & seat in the VST. Still has to get past the injectors...and that's gonna take a LOT of pressure to accomplish.

I have a "junk" tank out in the shop that I've attached a pressure gauge to. Fill it with 2 gal of fuel (3.3 gal tank) and let it sit outside in the hot Arkansas sunshine in July of this year. The sun was out ALL day, nary a cloud to be seen, temp was hovering around 101°F during the hottest part of the afternoon and was around 72 at night. The highest pressure recorded was 3.7 psi and the tank was no bigger than it was when I started (yamaha tank).

Metal tanks? With today's fuel, you'll lose a bunch of fuel to evaporation, and the stuff that's leftover is not good for carburetors or fuel injectors. The warmer and drier the climate, the worse the evaporation. Also as it evaporates, it loses heat (evaporative cooling effect)-and depending on the dewpoint of the air (around here it can be up around 80°F during the summers), the temp of the fuel can drop to the point where moisture will condense in the tank. It's a real problem here. Gasoline can boil at as low as 80°F (winter blend fuel) so any winter blended fuel disappears quickly, into thin air. I had a video at one point of a guys boat sitting outside in the sunshine with a temp probe stuffed down into the filler hole, fuel boiling, at 97°F actual temp. The longer it boiled the cooler it got. I took a sample, 500cc of it, in a measuring cup-left it sit for one hour and after one hour over 100cc of it was GONE, and there were water droplets in the bottom. The outside of the measuring cup was sweating and it was cool to the touch. I had all this on a video on my phone but I guess I done deleted it or moved it somewhere that I can't find.

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