Fuel for Thought

Tips, good practice and marine industry caution about biofuels

Fuel contamination is the single biggest cause of marine-engine failure. The potential risks increase as our boating activity decreases. This La Nina season on the eastern seaboard, characterised by above-average rainfall and brisk onshore winds, only exacerbates the infrequent use of marine engines.

Then there are all the other issues surrounding ethanol-blended petrol and biodiesel. Not to mention the fact you need to maintain your filters, fuel lines, tanks and system in general. And what about fuel additives?

Here are 10 tips to help avoid fuel-related problems with your outboard and/or inboard engine(s) during the course of the cooler months.

1. Fresh is Best

Generally, fuel less than three-months old is viable and that which has been lying in your tank for less than a month is safest. For this reason, most engine manufacturers advise filling up from service stations (and we should add busy boating clubs and marinas) that enjoy a high turnover.

The Boating Industry Association says more than 90 per cent of the 227,000-odd registered boats in NSW are trailerboats likely to take on fuel at roadside outlets. But beware.

The Outboard Engine Distributor’s Association recommends 30-days maximum storage of ethanol-blended E-10 fuel and less in hot and humid conditions. So if you have no choice but to use E-10 consider running your fuel down before storage.

2. But Keep the Tank Topped Up

The conventional wisdom with most forms of boating is to keep the tank at least three quarters full to prevent condensation on the internal walls. And it’s generally not good practice to run your tank down and draw-up the remnants in the bottom, which may include sludge.

Yet it’s been proven that the amount of condensation in a tank is really very slight and any major water contamination is probably due to dirty fuel.

But there’s a catch if you’re using an ethanol blend or biodiesel. These fuels are hygroscopic, meaning they will absorb water. You don’t want to leave a tank of E10 hanging around soaking up water for weeks or months on end. So run your tank down to less than half capacity if your using E- or B-blends.

3. Avoid E-10 and Biodiesel altogether

While most marine engine manufacturers say it’s safe to use ethanol fuel in Australia below 10 per cent content, ie. E-10, it’s even safer to avoid it altogether if you think your boat will sit stagnant for more than a month.

Regular unleaded is absolutely fine, but if you’re running performance-orientated bigger outboards then premium unleaded is go. It costs a bit more but it will also carry your boat a great distance and there’s nothing quite like the purr of high-octane fuel running through a big outboard or three.

4. Fuel filters

Every outboard runs a filter, even portable outboards have a small secondary filter under the cowl designed to trap larger debris. But in this day and age of uncertain fuel mixes, the advice is to fit some bigger primary filters, typically a 20 micron spin-on filter and an in-line 5 micron water separating filter.

If you are going to use just one filter consider a 10 micron number. Change or clean your filters every 50 hours, removing the filter with the aid of a strap wrench, and examine the contents of the housing or canister by tipping the fuel into a container. You can then assess the degree of contamination and, if it’s serious, drain your tanks.

Those of us with bigger diesel-powered boats tend to run decent inline water and dirt separating filters from the likes of Racor, as well as secondary spin-on filters on the side of the engine blocks. Draining your primary filters every few months is good practice.

With clear site canisters, you can make at-a-glance assessment of how much debris and/or water has collected inside.

When replacing screw-on filters don’t forget to grease the rubber o-ring to facilitate easy removal in future.

5. Check your fuel lines

Fuel lines, hand-primers and plastic connections have a finite life. Perhaps the most common cause of leakage is a split hose near a hose-clip nipped up too tight. Periodically check the system from tank to engine for leaks. After about 10 years, a fuel line constantly exposed the elements needs replacing, as might fuel filter assemblies suffering from corrosion.

6. Leaking fuel tank caps, deck fillers and breathers

We’ve all, at some stage, seen fuel leak from the cap on our portable tanks and smelt the result wafting back from the station wagon or under the splash well at the transom.

While overfilling is a common cause, so too are leaking screw caps. If you remove the cap you’ll notice there’s a small rubber o-ring in a recess. It’s not uncommon for this to deteriorate or go missing over time.

A leaky cap or, for that matter, deck filler on a bigger boat is an invitation for water to enter inside. Include an inspection on your pre-season checklist.

Keep breathers on portable tote tanks closed during transit, when exposed to the weather, but cracked ever slightly to allow for the expansion of fuel if protected from weather and, of course, open the breather when your outboard is in use.

7. Addicted to additives

Okay, we admit it: we’re addicted to additives.

Personally, I’m convinced that Diesel Power from Chemtech helps my twin Cummins 480hp run like a watch on beautifully conditioned fuel. There’s also a Petrol Power version.

Most major outboard companies offer fuel additives and some like Yamaha recommend adopting a multi-pronged approach using several of its proprietary additives where ethanol levels in fuel may exceed 10 per cent. Head that advice.

8. What about biodiesel?

The big bugbear here is, well, diesel bug, a kind of algae that feeds on water and blocks fuel systems. You can buy various de-bugging agents and additives, but you can also go a long way to preventing the scourge by avoiding biodiesel.

The Boating Industry Association and Boat Owners Association have joined forces to spread the good oil in a consumer guide at http://f.tlcollect.com/fr2/112/63015/BIA_biofuels_ART_14.09.11.pdf.

The guide says the addition of the “bio” components to mineral diesel reduces the shelf life of the fuel. Even in concentrations as low as five per cent of volume, the blended fuel can breakdown in as little as six months.

Breakdown of the fuel can result in accelerated engine wear, poor lubrication, and blockage of oil and fuel filters. For vessels voyaging offshore, especially yachts and others that turn over fuel slowly, this can be a serious safety issue.

Biodiesel exhibits poor oxidation stability and is an excellent medium for microbial growth, sometimes called diesel bug, which can itself cause blockages in lines and filters, while rubber and plastic components in the fuel system can be damaged by both aggressive forms of diesel bug, and the solvent properties of some bio-components commonly found in bio-diesel.

For safety and the protection of your engine and fuel system, insist that the marine-diesel supplier provide only 100 per cent mineral diesel. As diesel fuels with up to five per cent concentration of bio-components are not required to be so labelled, always ask the retailer to confirm that diesel fuel for marine use is bio-free.

9. How bad can it be?

There’s no doubt that ethanol-blended petrol and biodiesel can have catastrophic consequences on marine engines and their fuel systems. Consider the following extreme example from a Brazilian boater who posted his boating woes on a Suzuki outboard forum:

Point of interest - here in Brazil, it is a legal requirement that gasoline contains a minimum quantity of ethanol. At present it is 25%, and all car engines sold in Brazil have to be (de-)tuned by the manufacturer to run on the stuff. Not only this, but we are forced get a lot of our boating fuel either from (often illegal) floating petrol stations with dodgy tanks - lots of condensation and worse - or from guys in floating wooden houses who get it wherever they can and store it in plastic barrels.

Often the same containers are used for diesel and gasoline. To top it all, I know of one instance where a fuel station in Manaus had a delivery from its distributor which contained a significant quantity of animal fat. I believe Suzuki outboards here are also de-tuned and revs are limited. I know one guy who uses a coffee strainer to strain every drop of fuel that goes into his tank; me, I filter it as it goes in and then have to rely on my separator, plus low- and-high pressure filters, all of which I change every 100 hours without fail. I also have my injectors cleaned every 50-100 hours. So, um, yes - fuel is a problem!

10. Manufacturer Recommendations First

It might sounds like a cop-out to some, but the bottom line is to follow your manufacturer’s recommendations and, thus, remain under warranty. Some engines do demand premium unleaded, while some older outboards pre-1992 have incompatible components and fuel tanks with E-10.

The Bottom Line

Preventative maintenance, regular boat use (if only to go for a blast) and fresh fuel and filters are the keys to beating the dirty-fuel blues. Like most marine engine manufacturers and mechanics it’s just plain good advice to steer clear of ethanol-blended fuel and biodiesel. Why bother compromising your safety or enjoyment. Outboard Engine Distributors Association advice at http://www.oeda.com.au/ethonal_fuel_11.html.

We’re interested in your thoughts and experiences with the increasing availability of ethanol and biodiesel and its effects, if any, on your present and future boating activities?

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Fuel for Thought

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