Roberts: The lowdown on two-stroke outboards and the new EPA regulations

Published 12:00 am Monday, May 31, 2004

In 1998 the Environmental Protection Agency (EPA) began regulating outboard engine emissions.

This legislation affects U.S. and foreign built engines for sale in the United States. The new standard requires a 75 percent reduction in outboard emissions by model year 2006.

There’s been a great deal of confusion about how these regulations will affect the consumer.

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Here are some of the most common questions and, their answers:

4Will you have to buy a new engine?

No, the rules apply only to engine manufactures. The non-complaint outboards will no longer be &uot;manufactured&uot; and they will eventually be phased out.

4Will parts be available for my two-stroke outboard?

Yes, there were millions of two-stroke outboards sold and will continue to be sold until the June 15, 2005, deadline. Parts will be available for many years.

4Do the new 4-stroke and DFI engines cost more?

Yes, but they are more fuel-efficient, last longer, are easier to maintain and have no oil in the gas. They will save the consumer money in the long run. The estimated life of a carbureted two-stroke outboard is 1,000 hours compared to the four-stroke at 3,000 hours.

The average price difference between a Mercury 25 horsepower four-stroke and a two-stroke is about $700.

As you move up in horsepower, the margin grows wider. There is approximately $1,800 difference between a 250hp two-stroke Mercury EFI and the Mercury 250hp Optimax (DFI).

Manufactures of DFI and four-stroke outboards claim 35 to 45 percent better fuel economy over the non-complainant carbureted two-strokes.

Owners of the EPA-friendly engines readily agree with these claims. With the price of gas approaching two bucks a gallon, better fuel economy is a major issue.

The majority of saltwater and freshwater guides have re-powered, cutting their gas bills almost in half.

The high performance bass boat owners are very reluctant to make the switch from two-stroke to four-stroke.

The four-stroke engines lack the quick hole shot, blistering fast acceleration and top-end performance of the two-stroke outboards.

Most new high-performance boat buyers turned toward the compliant two-stroke DFI’s like the Mercury Optimax.

Mercury Marine recently completed &uot;Project X,&uot; a five-year long research and development project. Mercury’s multi-million dollar factory is dedicated to four-stroke technology.

The well-kept secret is a new breed of high performance outboards known as Mercury Verado. The Verados are super-charged four-stroke outboards designed for the high performance market.

Mercury claims the Verados offer a faster hole shot, better acceleration and throttle response than the DFI engines.

The Verados are equipped with a super-charger, electro-hydraulic steering and digital shift and throttle technology that does away with the old style push/pull cables.

Mercury has shifted its research from DFI to four-stroke engines because DFI outboards still release some emissions.

Rumors are floating around that the EPA may go after the Optimax and other DFI two-stroke engines. Therefore, Mercury has redirected its research from DFI to the super-charged four-strokes to take care of the high performance needs of the bass boaters.

Mercury has all so jumped ahead of the midrange four-stroke race with Electronic Fuel Injected (EFI) four-strokes.

Mercury offers 30, 40, 60 and 115hp EFI 4-stroke engines that start easier, idle smoother and run cleaner than the carbureted four-strokes.

Carburetors are the main source of problems with all such equipped outboards.

Weight is a factor. The four-stroke engines weigh more than two-strokes. A 25hp Merc four-stroke weighs 30 pounds more than a 25hp two-stroke. The Mercury Verado 250hp engines outweighs a 250 XS Optimax by more than 130 pounds. However, the weight difference will be less as four-stroke technology advances.

On July 1, 2005, the 2006 regulations will be in full effect. That’s only a little more than a year away.

At that time, the only outboard motors manufactured will be four-stroke and DFI two-strokes.

Carbureted oil injected, all EFI engines and non-oil injected two-strokes will no longer be manufactured. The smoky, noisy outboard motors that most of us grew up with will be a thing of the past.

The big plus is it will be better for all of us. Better for the environment, easier on fuel and they will last longer.

We’ll have much cleaner water in the future thanks to the new EPA outboard motor regulations.

Eddie Roberts writes a weekly fishing column for The Natchez Democrat. Reach him at