Managing ethanol / petrol mix for powerboats

You may well be ruining your engine ... It’s increasingly difficult not to buy petrol with 10% ethanol. This can cause more problems in boats than it does in cars, because we hang onto old boats longer than we do cars, and we use fuel less frequently and store it for longer.

Unlike cars, it’s not uncommon to see twenty-year old boats and motors still in use. Boat fuel can sit around for months between uses, in under-floor tanks, and plastic tubs in the back of the carport.

Standard unleaded fuel now mostly contains upto 10% ethanol .... and they do not need to tell you at the pump.

Boaters have four main problems with ethanol:

1. It absorbs water, so if it sits around in tanks for more than a few weeks, you are pretty sure to get water contamination. This can cause erratic running, and clog up fuel systems. Petrol floats on top of ethanol/water mix: if there is lots of water/ethanol mix in a tank, the petrol getting through to the engine will be of lower octane because the ethanol isn’t there, the engine will run leaner and hotter, and this can cause serious damage.
2. It’s an excellent cleaner, so the first few times you use it, especially in an older boat, you are sure to end up with a lot of sludge clogging up your fuel lines, tanks and engine.
3. It makes older types of rubber and plastics brittle or corrode away. Marine motors built around 2008 or later are designed to handle ethanol mix fuels, but older setups may develop leaks and cracks in fuel lines and fittings, and rubber and plastic particles in the fuel.
4. Older fiberglass fuel tanks react with the ethanol and go sort of soft and runny.

What’s the solution? Buy a new boat or motor? Yes, well, mortgages, teenagers – it’s not a solution for most of us, and even the newest boats can still get water in their tanks. Don’t buy ethanol/petrol fuels? Best to stock up now, that’s all that will be on the market in a year or two. But with some sensible precautions and changes in practice, you can minimize these risks:

1. Don’t store fuel for more than two weeks. Don’t top up at the end of the day, wait till your next outing. If you won’t be afloat for a few weeks, drain the tanks (or as a long second best, if you absolutely must, fill them right up so there is no air to help condensation). Only buy fuel from trusted sources with high turnover, so there is less chance of buying water pre-mixed with your fuel. Twin tanks? Fill each at a different marina or petrol station.
2. Fit one or more fuel-separating filters, and check them before, during and after every outing.
3. If your boat or motor is more than a few years old, have the entire fuel system professionally cleaned, and all lines and fittings inspected and replaced if necessary. Inspect all fuel lines and fittings every few weeks.
4. If you have fiberglass tanks, have them professionally inspected – you may need to replace them.

Most of the engine manufacturers have specific information and advice on their web sites – just Google ‘ethanol’ and the make of your engine. 

Of course, you could always buy an Etchells . . .

PS.

Buying Premium fuel may be an option, I don't believe it contains ethanol (yet). Our Yamaha support manager at Pittwater Marine, Peter Finch, says that premium unleaded is fine in Yamaha 4-strokes, and even with the latest motors, ethanol mix can still cause long term problems with plastic fuel tubs, fuel lines and primer bulbs.