How to Maintain Your Boat’s Tanks

How to Maintain Your Boat’s Tanks

Fuel, water and waste tanks accumulate gunk over the years.Get rid of that stuff before it damages something expensive.

Doctors tell us it’s important to lower our cholesterol to keep our blood running freely and prevent a clump of fat from breaking loose and clogging something essential. The same is true of boats: Fuel, water and waste tanks will collect gunk over the years that can get churned up and find its way into the plumbing or the engine. Nothing ruins a fine summer afternoon faster than an engine dying from fouled injectors, or a waste tank leaking fumes and effluent into the bilge. Act beforehand to prevent this: Clean your tanks while the boating season’s still young.

Dirty fuel tanks cause the most trouble, so deal with them first. Dirt, water or biological gunk in gas or diesel tanks can be sucked into and clog the engine’s delicate fuel system—more common now that many engines use high-pressure fuel injection. Fuel has to be absolutely pristine. Folks who remember the problems caused by the change from pure gasoline to ethanol blended fuel can vouch for this: “Older boats had dirty tanks, and ethanol is technically a cleaner,” said Jim “the Boat Guy” Valiante, a mobile mechanic from eastern Connecticut. “It would remove the dirt and growth from the inside walls and pass it through the fuel system.” The result was clogged fuel filters, carburetors and injectors.

Ethanol also bonds with water, which can cause the ethanol to drop out of solution with the gasoline; the result is a layer of ethanol/water under the gas. This is called “phase separation.” When enough water collects under the fuel, it can be drawn into the engine, so installing a high-quality fuel filter/water separator is essential. Valiante said phase separation can happen in as little as 15 days unless you add fuel stabilizer at every fill-up, which might prevent your having to clean your fuel tank manually—and cleaning with chemistry is much less hassle. “We rebuild over 50 carburetors a season from people who do not treat their fuel,” Valiante said. He recommends Star brite’s Star Tron; other choices include Liqui Moly Marine, Sta-Bil and ValvTect ethanol gasoline stabilizers, and there are many others.

If you’ve just acquired a pre-owned boat, call in a pro to clean the tanks before you even attempt to start the engines, especially if the boat has been sitting in the “For Sale” lot for a couple of years, giving bacteria, fungi and other critters plenty of time to breed in the fuel. Along with biological invaders, there’s undoubtedly dirt and water collected at the bottom of the tank. You need to get all this stuff out. Once you have clean tanks, keep them clean with regular use of fuel treatments, and by using your boat often; don’t let fuel sit in the tank, but take the boat out and burn it. Everything else on the boat works better with frequent use, too.

Cleaning Tanks Can Be a Pain

There’s an easy way and a hard way to clean a tank. The easy way involves writing a check to someone who has the equipment and expertise to do the job. The hard way is to do it yourself. A few minutes of Googling will hook you up with a professional who will not only do the job properly, but will also bring storage containers to hold any fuel that has to be pumped out. Your engine sometimes decides to pack up right after you leave the fuel dock, so you might have 50 or 100 or however many gallons in the tank that must be dealt with. If the fuel can be salvaged, a pro will filter it before pumping it back into the tank; if not, he’ll know where to get rid of it. I think it’s money well spent. If you disagree, you can do it yourself with fairly basic equipment—but while it’s usually less costly in dollars, DIY’ing the job can be more difficult and frustrating than it appears at first.

The first problem is access: How do you get at the sludge, water or whatever that you want to remove? Not many tanks on the kinds of boats that most of us own have access ports, and if they do, they’re minimal. If your tank has multiple ports and sufficient clearance above the ports to provide usable access to the inside of the tank, you are indeed fortunate. The ABYC doesn’t require access ports on any tanks, but if a manufacturer installs ports, they have to meet ABYC requirements, such as: “If inspection access opening(s) are installed, they shall have a minimum diameter of 4.75 inches (120 millimeters) at suitable position(s) for cleaning and inspection of the lowest part(s) of the tank. The access opening(s) shall remain accessible when the tank has been installed in the craft.” This requirement is for diesel fuel systems; the requirement for gas is less detailed, the most important stipulation being that all openings must be on top of the tank. Access ports in water and waste tanks are basically not addressed.

If there’s no port, there’s usually access to the fuel-gauge sending unit in the tank. Removing the sending unit opens a hole large enough to insert a hose or suction pipe. Cleaning the sides of the tank will have to be left to a solvent added at the next fill-up; this route will require frequent checking of the primary filter, which will soon be clogged by gunk. A vacuum gauge is a big help here—a higher than normal vacuum means the filter is clogging, so a vacuum gauge is a worthwhile addition to your fuel system.

Even if an access port is installed, baffles, placed inside the tank to minimize sloshing of the contents, usually make it impossible to reach all of the tank. With luck, the port will be over the lowest point of the tank, so at least you can suck out any water and most of the solid debris. Professionals have pressure washers with special spray tips for cleaning baffled tanks; it’s more efficient than using a solvent, you won’t have to keep replacing filter cartridges, and the money you save can go toward the fee.

Don’t Be Penny Wise and Pound Fuelish

Cleaning out a diesel tank is pretty safe, but gasoline fumes can explode. Don’t be ‘fuelish’: Take the necessary precautions to prevent a spark sending you to Kingdom Come. Use only non-sparking manual pumps to remove gasoline, or ignition-protected electric pumps intended for marine use. Beckson Siphon-Mate pumps are simple, reliable and suitable for gasoline and diesel. Once you get the flow started, it keeps going on its own. Like all siphons, this works only if the outlet is lower than the intake—easy if the boat’s out of the water, maybe not so much when overboard. Otherwise, you’ll have to pump by hand until the tank’s dry, or rig a suitable, and safe, electric pump.

Sometimes it’s more effective to use a pipe rather than a flexible hose to suck the dregs from the bottom of the tank, because you can control the placement of the pipe more accurately. When working with gasoline in a metal tank, choose a pipe material that’s non-sparking—even stainless steel can spark, so don’t stick a galvanized pipe into a stainless tank to suck out the last drops of gasoline. A better choice might be to zip-tie a fuel-approved rubber or plastic hose to a wooden dowel.

If you open the tank, by removing an access panel or the fuel sender, for example, use a replacement gasket when closing it again, to minimize the risk of a poor seal that allows fumes to escape. Use new, all-stainless marine-grade hose clamps when re-attaching any hoses; don’t re-use hose clamps. Be extra-fastidious when working with gasoline; a diesel leak is annoying, but a gas leak, liquid or fumes, is dangerous.

Some folks “polish” their fuel to remove impurities; polishing is simply running the fuel through a series of filters and water separators and then returning it to the tank. Diesel-powered yachts with big tanks often have polishing systems built in. It’s less common to polish gasoline. I’d call a tech with a portable unit to polish my fuel, but the equipment is pretty simple; you can build your own, if you insist. You’ll need a pump, hoses, a 30-micron fuel filter to strain out the coarse contaminants, a 10-micron fuel filter/water separator for the finer stuff, a length of pipe to reach down to the bottom of your fuel tank, and assorted bits and pieces to hook it all up.

Fill-Rite’s U.S.-manufactured RD812NH fuel-transfer kits have much of what you need, including a shut-off nozzle for refilling the tank. Gasoline flowing through a hose can generate static electricity, which is why we’re taught always to prevent static-electric sparks by keeping the nozzle in contact with the grounded metal fuel fill. The Fill-Rite kit includes static-preventive hoses (wire wrapping prevents static build-up) and an aluminum nozzle for just this reason. If you’re cobbling together a fuel-polishing system to use with gasoline, use similar hoses to conduct any static charge to a metal nozzle or fitting, which safely discharges it into the grounded fuel fill.

The Fill-Rite specs don’t mention ignition-protection specifically, but list the motor as “certified explosion-proof” by UL and other agencies; I spoke with a tech rep at Fill-Rite who said “they don’t spark.” The kit lists for $436 on the company website, but the filters, water separator and related plumbing are not included. By the time you add them, you’re looking at $500 or so. Once the fuel is clean, keep it that way with appropriate additives.

Waste and Water

You might think that once your fuel tanks are clean, your problems are over. Not according to Jim Valiante: “The single biggest tank issue I encounter is a dirty water tank,” he said. The tank sits in summer warmth and grows algae, and when it’s time to empty the tank and winterize the water system, “the pump just runs and runs. We find the nastiest slime caked all over the strainer. We clean it and run the system and inevitably it clogs again.” The solution, said Valiante, is to add a cup of bleach to the water tank with each fill-up to prevent algae growth. Typically, during the season the water starts to smell from algae, but the boat owner isn’t able to solve the problem on his own, so he doesn’t use the water system and it just gets worse.

If you don’t want to use bleach, there are many proprietary additives you can dump into your water tanks. Star brite’s concentrated AQUA Water Shock cleans the water after winter storage, improving the taste and removing foul smells. The company’s Tank and System Flush keeps the water tank and plumbing clean. The shelves of your marine chandlery are loaded with similar products from different companies—but once the tank is cleaned, I think Valiante’s cup of bleach cure will be hard to beat, and it costs almost nothing.

Waste tanks often smell so bad, you’re tempted to go back to using a bucket, especially if you’re still flushing with bacteria- and algae-laden salt water. Freshwater-flush heads create much less odor. Cleaning a holding tank is easy: Simply pump it out, fill it with fresh water, pump it again and add a sanitation system cleaner. Most cleaners use chemicals, but Raritan’s K.O. Kills Odors adds aerobic bacteria to the tank, which the company says is superior to chemical control. The aerobic bacteria displace the smelly anaerobic bacteria, so the stink goes away, but enough live bacteria are left to break down and emulsify solids so they can be pumped out. Chemical treatments kill all the bacteria, leaving none alive to deal with the waste, which ends up caked on the bottom of the tank and the smell soon returns. Raritan makes other products to clean sanitation hoses and toilets, while, again, there are many products from other companies for you to try. Or you can go back to the bucket to “catch and release.”

Once your tanks are all cleaned, you can start enjoying your boat again. With luck, you’ll get through the season without any fluid-based mishaps, and can concentrate on lowering your cholesterol. Maybe there’s a way to do it without giving up cheeseburgers; if we find one, we’ll cover it in a future Boatyard.

View the original article to see embedded media.

This article originally appeared in the June/July 2024 issue of Power & Motoryacht magazine.


Boat Lyfe