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[outboardmotor]

Fuel efficiency and environmental concerns are driving outboard motor development and innovation, but an alternative fuel source for outboard motors is decades away according to the experts. Despite this, outboard manufacturers are determined to deliver cleaner, greener, quieter and more fuel efficient engines using existing technologies.
Whether it’s for cost savings, environmental considerations or ease of use, many boat owners want to improve their boat’s fuel efficiency. Innovative new technologies and fuel sources developed by car manufacturers aren’t suitable for marine use. Hybrid cars might be growing in popularity but according to marine experts the batteries needed to power hybrid engines are too heavy and vulnerable to saltwater damage to be used on boats.
Other fuels such as hydrogen, diesel and LNG pose power to weight and accessibility problems, and the outboard motor market isn’t big enough for manufacturers to recoup the R&D investment needed to develop petrol-alternative outboards. In the absence of a revolutionary new fuel source, outboard manufacturers are focused on developing the cleanest and most fuel-efficient engines that current technologies will allow.
Efficiency Replacing old two-stroke engines is the best way that boat owners can reduce their fuel bills, especially for offshore fisherman and other people who do many miles at medium to high speed. New age DI two-stroke and EFI four-stroke outboard motors are significantly more fuel efficient than traditional two-stroke engines, as well as being kinder to the environment. Four-stroke engines are the cleanest horse power outboard marine motor, as the intake and exhaust valves are never both open at the same time, ensuring that unburned fuel does not escape the combustion chamber.
Mercury Outboards are generally considered some of the most fuel efficient motors on the market. Their flagship Verado range achieved a twenty per cent improvement in fuel efficiency by reducing friction, which helps the engines to run more smoothly, efficiently and economically.
Old-style two-stroke carburettor motors are becoming very unpopular, and some people are even campaigning for them to be banned based on their poor fuel efficiency, since 20-30% of fuel used to power these engines never gets burned and is emitted into the water and air. Sales of traditional, large fuel-thirsty two-stroke engines have fallen in recent months thanks to fuel price increases.
Two-stroke engines with direct fuel injection are not as clean as four-stroke engines, but they are cleaner than 2-stroke carburettor engines, as they spray fuel into the cylinder after a piston covers the exhaust port.
Optimisation
Local boat and outboard motor dealers should be able to help consumers rig their boat up for maximum fuel efficiency. It’s important that a boat is propped correctly, has the right type and size of engine fitted, and is driven correctly to ensure maximum performance and efficiency.
Equally, owners need to ensure that they “trim” their boat properly, as otherwise hull performance will be compromised and fuel efficiency will drop. Also running any engine at full noise will result in poor fuel efficiency. Outboard makers tend to recommend that boats should cruise at around 3000-4000rpm, where the majority of motors are at their most fuel efficient. Filling up with premium fuels is also recommended to minimise petrol use.

[Charlie Jones]

All in all, very good post.

Was interested in this though

"Mercury Outboards are generally considered some of the most fuel efficient motors on the market."

In over 7000 miles of coastal and Bahamas and Mexican (Yucatan and south) cruising in the last three years, I began noticing the brands of outboards. What I saw was that Yamaha OWNS the Gulf coast, east coast, Mexican and Bahamian markets, something like 4 or 5 to one. Mercury runs a distant second, and all other brands combined fall to third place.

Personally I own two four stroke Yamaha's (an 8 hp and a 4 hp) and love them. Great fuel economy and so far, total reliability. Two strokes are dead as far as I'm concerned except for perhaps very small ones, like 2 and 3 hp, for use on dinghies. The 4 strokes have a weight problem to over come there.