Few topics get our commenters more riled up than ethanol.

Both sides weigh in with fervor and passion, debating energy security versus agricultural policies and costs, comparing studies on wells-to-wheels carbon dioxide profile versus the impact on older engines, and more.

But marine users in particular seem to view ethanol as a hot button.

DON'T MISS: Senate Bill Introduced To End Ethanol Mandate For Gasoline

The issue in boat engines turns out to be twofold.

First, older marine engines are not designed to handle the increased corrosion and solvent effects from even the small percentages of ethanol (up to 10 percent) now found in much pump gasoline.

In that respect, they join small utility engines in chainsaws, lawn mowers, and other power equipment, many of them far older than a huge proportion of cars on the road today.

Second, the water-absorbing properties of ethanol pose a particular challenge to boats that sit stationary in storage for many months each winter.

Rolls-Royce Merlin powered Aeroboat (Image: Claydon Reeves)

Rolls-Royce Merlin powered Aeroboat (Image: Claydon Reeves)

Adding water to any fuel vastly changes its characteristics.

At a certain saturation, the water and ethanol may mix together, separate, and sink to the bottom of the tank, leaving the layer of gasoline floating on top.

The simpler (and less expensive) carburetors or fuel-injection systems on many such engines can't adjust for that as more sophisticated modern automotive systems may.

Most marine and small-equipment engines are far more primitive than car engines, and have little or no modern emission-control equipment.

ALSO SEE: Congress Actually Ends Taxpayer Funding Of Ethanol Subsidies (Dec 2011)

It was largely the rise of emission limits for passenger vehicles that led to increasingly precise fuel metering and delivery, along with ever more complex combustion-control software.

If you look at your gasoline lawn mower, or perhaps your boat engine, you'll see a carburetor of the sort that vanished from passenger cars by the early 1990s.

But between the two challenges, boat owners have found that ethanol can do serious damage to a boat stored over a long snowy winter.

Fiberglass gas tanks can start to disintegrate; one experienced boat owner says, "It can be fatal, in as little as three to four years, for gasoline boats with fiberglass tanks."

Non-ethanol gasoline pump

Non-ethanol gasoline pump

"There was a flutter in the marina workshops several years ago to replace fiberglass tanks with aluminum or stainless-steel tanks," he continues, "but that's harder than it might sound; fiberglass tanks are built early in hull construction, and are regarded as structural members as well as tanks."

Also, accumulated debris in the tank or fuel lines can be loosened, letting it reach the engine. Rubber seals in older engines weren't designed to resist ethanol either.

Then there's the potential for separation of ethanol and water mixed together in gas tanks or fuel lines, potentially damaging engines that can't run smoothly on the watery fuel.

One solution to these problems, highly recommended by marine experts, is to add a fuel stabilizer and conditioner to the boat before storage.

MORE: Electric Boats: As In Cars, Battery Power Offers Advantages On The Water

It's important to run the engine long enough to ensure it is circulated through the entire fuel system.

A better solution, and the one forcefully advocated by many commenters, is to avoid gasoline that contains any ethanol at all.

So-called G100 is still offered at some marinas (and the occasional gas station), though for road use, it's far rarer than it was 10 or 15 years ago.

(It too should still have a fuel stabilizer added, according to our local shade-tree mechanic colleague.)

For more on winterizing boats, see Ethanol and Winter Storage, from the marine website Soundings.

[With thanks to reader Rusty13 and our anonymous boat owner]


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