Taking care of an evinrude outboard motor gas tank can feel like a part-time job sometimes, especially if you're running a vintage setup that's been in the family for decades. There's just something about those old Evinrude engines—they're workhorses, but they're also a bit particular about how they get their fuel. Whether you're dealing with a classic 1950s pressure tank or a more modern plastic portable tank, getting the fuel delivery right is the difference between a great day on the lake and being the person waving for a tow back to the dock.
The Old School Pressure Tanks
If you've got one of those vintage 5.5hp or 10hp OMC motors from the mid-50s, you probably know all about the "pressure tank" system. These are the heavy, metal, two-line tanks that are becoming harder to find in good shape. Unlike modern systems that use a fuel pump on the motor, these old setups actually pump air into the evinrude outboard motor gas tank to push the fuel up to the carburetor.
The most common headache with these is the seal on the tank head. If that big rubber gasket is cracked or dry-rotted, the tank won't hold pressure. You'll be pumping that manual primer button until your thumb is sore and the motor still won't start. If you're lucky enough to own one of these, keep those gaskets fresh. And for heaven's sake, don't lose the dual-line hose. Buying a replacement hose assembly these days can cost almost as much as the motor itself.
Moving to the Single-Line System
Most people reading this are likely using the more common single-line evinrude outboard motor gas tank. This is the standard "vacuum" style where the motor's fuel pump sucks the gas out of the tank. While these are much simpler than the old pressure systems, they aren't without their own set of quirks.
The most important part of this setup isn't actually the tank itself, but the connector. Evinrude and Johnson (OMC) used a very specific clip-on connector that's different from Mercury or Yamaha. You've probably noticed that little metal pin and the O-ring inside the connector. If that O-ring gets a tiny nick in it, the pump will suck air instead of gas. It's like trying to drink through a straw with a hole in it—you'll get a lot of bubbles and not much else. I always keep a few spare O-rings in my tackle box because they're cheap and save a lot of frustration.
The Battle Against Ethanol
We can't talk about an evinrude outboard motor gas tank without mentioning the elephant in the room: ethanol. If you're buying regular pump gas with 10% ethanol, you're basically inviting a chemistry experiment into your fuel system. Ethanol loves to soak up moisture from the air. In a boat, where it's literally surrounded by water, that's bad news.
Over time, that moisture-laden fuel settles at the bottom of the tank (a process called phase separation). If your boat sits for a month, you might be trying to start your engine on a cocktail of water and gunk. Even worse, ethanol is a solvent that can eat away at old rubber fuel lines. If your lines feel soft or "mushy," they're probably disintegrating from the inside out, sending tiny black flakes of rubber straight into your carburetors. If you can find ethanol-free "REC-90" fuel, use it. Your Evinrude will thank you.
Cleaning Out the Gunk
If you've pulled an old evinrude outboard motor gas tank out of a barn, don't just rinse it and go. You'd be surprised what can live inside a fuel tank. I've seen everything from rust flakes to dead spiders and even mysterious "jelly" formed by old oil.
A trick I've used for cleaning out old metal tanks involves a handful of nuts and bolts. Empty the tank completely, throw in a cup of degreaser or fresh gas, and toss in those nuts and bolts. Shake that tank like you're trying to win a prize. The hardware acts as an abrasive to knock the rust and varnish off the interior walls. Just make sure you count them going in so you know they all came out. After a few rinses, you'll have a much cleaner environment for your fuel.
Troubleshooting the Primer Bulb
Sometimes you think the evinrude outboard motor gas tank is the problem, but it's actually the primer bulb in the middle of the hose. These things are simple, but they have a little check valve inside that only lets fuel flow one way.
Here's a tip that catches a lot of people off guard: when you're priming the bulb, hold it vertically with the arrow pointing up toward the sky. This helps the check valve seat properly so the fuel actually moves toward the engine. If the bulb stays flat after you've squeezed it, you've likely got a clog in the tank's pickup tube or the vent is closed.
Don't Forget the Vent
Speaking of the vent, this is the simplest part of an evinrude outboard motor gas tank, yet it causes the most "breakdowns." Most portable tanks have a little screw-top vent on the gas cap. If you forget to open that vent when you're running, the fuel pump will create a vacuum inside the tank. Eventually, the pump won't be strong enough to pull any more gas, and the motor will just bog down and die.
It's a classic move: the motor runs great for ten minutes, then dies. You wait a few minutes, it starts back up, then dies again. If that's happening to you, check the vent. It's the first thing I look at when someone says their motor is "starving for fuel."
Plastic vs. Metal Tanks
There's a lot of debate among boaters about whether to stick with the original metal evinrude outboard motor gas tank or switch to a modern plastic one. Metal tanks are tough and they don't "breathe" or smell as much, but they eventually rust. Once they start pitting on the bottom, it's a losing battle.
Plastic tanks are great because they never rust and they're lightweight. However, the newer "EPA-compliant" plastic tanks can be a real pain. They don't have traditional vents because of emissions laws. Instead, they're designed to swell up like a balloon in the sun. This internal pressure can actually force fuel into your outboard while it's sitting, potentially flooding the engine or causing leaks. If you use a new plastic tank, I highly recommend disconnecting the fuel line from the motor when you're not using it.
Proper Storage Habits
If you're putting your boat away for the season, how you handle your evinrude outboard motor gas tank matters. Some guys swear by topping it off to prevent condensation. Others say you should drain it completely.
Personally, I like to leave the tank mostly empty and add a heavy dose of fuel stabilizer to whatever is left. If you leave a tank half-full without stabilizer, that gas will likely be "skunky" by springtime. You'll know it the second you open the cap—it smells like old varnish instead of fresh fuel. If it smells like that, don't even try to run it. Just take it to a hazardous waste disposal and start fresh. It's much cheaper than a carburetor rebuild.
Final Thoughts on Fuel Safety
At the end of the day, your evinrude outboard motor gas tank is a bomb in a box. It sounds dramatic, but gasoline vapors are no joke, especially in the confined space of a boat. Always check your hoses for cracks and make sure your clamps are tight. If you smell gas while you're out on the water, stop and find the leak.
Most of the time, keeping your Evinrude running perfectly just comes down to the basics. Keep the fuel clean, keep the air out of the lines, and make sure that tank is venting properly. If you do those three things, that old motor will probably keep humming along long after the newer, fancier ones have headed to the shop. There's a reason you still see so many of those vintage Evinrudes on the water—they were built to last, as long as you treat their fuel system with a little respect.