Green Outboards: The new "Environmentally Friendly" Outboards

Environmentally Friendly Outboards
With the increase in environmental pollution and in a quest to reduce harmful emissions, the various environmental agencies have been coming out with stricter regulations on an ongoing basis.

One of the first targets, for powerboaters, is the good old 2 stroke outboard. For years these reliable, relatively simple workhorses of the waterways have soldiered on largely unchanged. Sure, they have been refined, look more modern, and have updated ignition and fuel systems, but they still burn oil, create clouds of smoke when started, and pollute. That is going to change. With new regulations, outboard manufacturers are being forced to find new ways of producing the same horsepower with less pollution.

There are other benefits to this new technology, in addition to the reduced emissions. Some of these benefits can include better fuel economy, quieter engines, and reduced operating costs.

"Green" Outboards
What are some of the approaches that the manufacturers are taking to make their outboards more environmentally friendly?

The current crop of 2 stroke outboards are better than their predecessors from even ten years ago, thanks to better fuel management, improved ignition systems, and oil injection. There is, however, a limit to what can realistically be done to reduce the emissions of the "traditional" 2-stroke engine. The next step, from most of the manufacturers, is some form of "direct injection" technology for a 2-stroke, as well as a selection of 4-stroke outboards.

2-Stroke vs. 4-Stroke
Which is better? That depends on what you need the outboard to do. 4-strokes are generally quieter, smoother running, lower maintenance and lower polluters than even direct injected 2-strokes. They are also (usually) heavier with poorer acceleration.

In response to the requirements of some powerboaters, specifically boaters looking for speed, many of the manufacturers are offering direct injected 2-stroke outboards in larger horsepower outputs in addition to 4 stroke outboards in the smaller categories.

The 4-stroke engine produces lower emissions than a 2-stroke for a number of reasons. They don't burn oil, and they have far better control of the air and fuel flow than a 2-stroke. The new direct injected 2-strokes, however, have reduced this gap by providing precise control of fuel and oil consumption, reducing emissions by up to 80% over conventional 2-strokes. Fuel consumption can also be reduced by up to 33% combined with a 50% reduction in oil consumption, all while retaining the power of a 2-stroke that boaters are expecting. Emission reduction aside, these improvements can add up to significant reductions in operating costs.

Direct Injection - What is it?
Simply stated, direct injection involves injecting a precise amount of fuel into the combustion chamber, in contrast to having "approximately" the correct amount of fuel being drawn in along with the air flow. Also, with direct injection, the fuel is better atomized than with standard 2-strokes, resulting in a cleaner, more complete burning of the fuel.

The major outboard manufacturers seem to be taking a variation of 2 different approaches to direct injection, as outlined below.

High Pressure Injection

FICHT Ram Injection - OMC (Evinrude and Johnson)
This system involves the fuel being inject into the cylinder by means of a mechanical "plunger", at a pressure of up to 500psi. The published results of this system (on OMC's website) promise up to an 80% reduction in emissions over conventional 2-strokes. OMC offers this system on V4 outboards from 75hp to 115hp, and on V6 outboards from 135hp to 250hp.

HPDI - Yamaha
High Pressure Direct Injection (HPDI) involves the use of a very high pressure (700psi) fuel pump that injects the fuel directly into the cylinders. This sytem is offered on a range of Yamaha outboards from 150hp to 200hp.

Low Pressure Injection

Optimax - Mercury
The Mercury Optimax system uses a 2 stage direct injection system, where fuel is first staged in a small chamber outside of the actual combustion chamber, and then forced into the combustion chamber by an 80psi burst of air. This system is available on a range of outboards from 135hp to 225hp.

TLDI (Nissan/Tohatsu)
The Nissan/Tohatsu TLDI (Two stroke, Low pressure, Direct Injection) system also utilizes a low pressure system for injecting the fuel into the combustion chamber. This is available in 50hp and 90hp models.

Which system is best? Time will tell, but if you believe what each of the manufacturers claim on their websites, you'll be thoroughly confused. Predictably, each has reasons why their system is better.

The best advice I can give? Talk to owners of the outboards you are considering, and find out if they are happy with them.

4-Stroke Outboard Manufacturers
Most of the major manufacturers offer a variety of 4-stroke outboards. The leader for years of course has been Honda, with their entire model line consisting of 4-strokes from 2hp to 130hp. Mercury offers 4-strokes in a range from 4hp to 115hp. OMC (now owned by Bombardier) has 4-strokes under both the Johnson and Evinrude brands ranging from 5hp to 70hp. Nissan and Tohatsu have smaller 4-strokes only from 4hp to 18hp. Yamaha has an extensive line of 4-strokes, ranging from 8hp to 115hp. Suzuki has a similar range with 4 strokes from 9.9hp to 115 hp.

If you are looking for a new outboard, be sure to consider one of the newer, environmentally friendly models. There are a number advantages - in addition to lower emissions