posted 10-17-2003 01:11 PM ET (US)            

"Hey Does that have a HEMI?"

I love my 4-stroke. Reliable quite and speedy.

Sips gas really slow like a Bar girl sips beer in the Phillipines.

I cannot hear my motor when running over my 5 gallon self made Bait well.

posted 10-18-2003 11:28 PM ET (US)            

As regulatory control over recreational outboard motor exhaust gas emission is increased, use of simple carburetor induction will probably begin to decrease.

The EFI approach seems to have completely taken over the automotive engine. The last car I can recall that had carburetors was a HONDA Prelude from the early 1980's. Thus when I see a 4-stroke outboard motor with carburetors I think of engineering from c.1980, not engineering from year 2003.

Since outboard motors are usually operated in fairly temperate zones, they work rather well with simple carburetor set ups. We usually are not trying to start and run our outboard motors at temperatures like minus-10-degrees. Thus you don't need to pre-heat the air to them or to modulate the choke as the engine warms up. All these things are typically done in automotive applications to compensate for the limitations of the carburetor.

posted 10-19-2003 12:14 PM ET (US)            

quote:

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EFI engines are more sophisticated and lend themselves to more control of the combustion process by microprocessor. This permits the engine designer to have more control over the exhaust gas emissions...

It does not have, as far as I can tell, any intrinsic advantage that would make it run faster or get better fuel economy than a carburetor-equipped engine of similar horsepower.

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Improving emissions is improving efficiency. The emissions of unburned hydrocarbons are molecules that didn't get to burn or burn completely and thus produce power and thus miles per gallon. Carbon monoxide instead of carbon dioxide indicates incomplete combustion. Emissions from carbureted cars and motorcycles can be lowered simply with a catalytic converter. There are carbureted bikes still in production that meet CARB and EPA standards. Admittedly these aren't quite as stringent as those for cars, but that is mostly in the area of oxides of nitrogen, until recently. Fuel-injected engines offer better control of mixture, and increase the efficiency of converters, but that's not the only reason for EFI. Corporate Average Fuel Economy (CAFE) is the main reason you don't see carbs on cars any more.

I'm not an engineer, but my hobby for a number of years has been motorcycle performance. That includes significant time on chassis dynos with fuel/air meters and eddy current brakes for steady state part throttle loading, in addition to WOT performance determined by acceleration of a drum. Most of that experience is with tuning carbs, but a little of it includes programming electronic fuel injection. Although motorcycles (and cars) have to deal much more frequently with throttle position changes, and have to address that through accelerator pumps on carbs, the WOT and part-throttle cruise is similar to the requirements of outboards. Where fuel economy is of no or slight concern, it's easy to make power by throwing fuel at the problem... to a point. But getting that power efficiently, i.e. having a setup that gets good performance in all areas of operation AND gets good mileage, is certainly more of a challenge.

With a carb, you only have a very few number of circuits to adjust and each, primarily the main, covers a HUGE number of combinations of engine speed and throttle position, not to mention air temperature and barometric pressure (density and oxygen content) etc. With a carb, you can't just tune for an average air/fuel mixture for all of these combinatins because of the danger of engine-damaging detonation that can occur with the mixtures on the lean side of average. So you jet for an average on the rich side, which means in most cases, you're pushing fuel through the system that will not contribute to power, and that reduces economy. With EFI, you're can much better tune much smaller ranges of operation, eliminating wasted fuel in many.

I won't even get into the advantages of port injection when it comes to reducing the condensation and aggregation of fuel droplets in an intake manifold, be they from a carb or throttle-body injector. The smaller and greater the number of droplets from a given amount of fuel, the more surface area available for combustion, and it's only surface area that combusts. Injectors excel at this.

I might agree with the statement that EFI won't make more, or at least significantly more, power at WOT. But I'll strongly disagree that EFI doesn't improve part-throttle performance or overall economy. I've seen too much evidence to the contrary.

posted 10-19-2003 04:06 PM ET (US)            

1. I have to lift a choke lever and hold at the desired high RPM for cold starts.

2. I've had to synchronize my carbs at the 20 hr. break-in service.

3. A carburator adjustment CHECK is called for every 100 hours with or without possible adjustment.

A friend of mine has an identical Whaler as mine but has a Suzuki 90 EFI on his boat, I have the BF90. Performance is almost identical as is fuel consumption.

posted 10-19-2003 05:39 PM ET (US)            

• Programmed Electronic Fuel Injection
4 Fuel Injectors and a Common High Flow Throttle body deliver the precise amount of fuel/air to each cylinder.
Benefit
The result is easy starts, instant throttle response with superior fuel efficiency.

posted 10-20-2003 12:11 AM ET (US)            

I don't know if most outboards with EFI have exhaust gas sensors and use a feedback loop. I think Yamaha had a model that does that, the OX-66 engine was it?

Very good information re more sophisticated fuel mixtures, etc. Also good report on current carburetor technology.