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09-19-2012, 10:43 PM
What is meant by the term “Electronic Fuel Injection”?

According to SC’s marketing materials, the Indmar engine in my ’07 Outback is equipped with Electronic Fuel Injection.

Chapter 6, Maintenance, in Indmar’s operator’s manual states: “The fuel system consists of fuel lines, fuel pump, and an unused fuel recovery system.” It also states: “The carburetor on your engine has been carefully adjusted at the factory and has had sealing caps applied to the idle mixture screws to prevent further adjustment.”

Chapter 8, Troubleshooting, infers in several places that some Indmar engines are fuel injected and states clearly that some are carbureted.

Nowhere in the manual is there any specific discussion of injectors or fuel injection. Further, on my Outback I don’t see fuel injectors or evidence of fuel injectors like on a car engine.

I’m not a gearhead, but it seems to me that engines are either carbureted or fuel injected. If there is a third kind of fuel system on these boat engines, I am not aware of it.

As it applies to my boat, someone who knows please tell me what kind of fuel system (carbureted or injected) is on the engine and what SC means by Electronic Fuel Injection.

Thanks. - Deerfield

09-19-2012, 10:49 PM
Basically what you and I have are Throttle body injection...Basically a slightly modified carb,with full electronic ignition,systems... I,m not a mechanic either.maybe someone ,will go further with this reply?

09-20-2012, 12:34 AM
throttle body injection TBI will have 2 or 4 fuel injectors sitting atop the 2 or 4 barrels of your throttle body or bare stripped down carb. All injectors are electronically controlled depending on different sensors the first being a throttle position sensor TPS. MPFI will have fuel rails supplying the injectors which feed fuel thru the intake manifold just above the intake valves and again the amount is regulated by the TPS. With the cat engines there are oxygen sensors which measure the amount of oxygen in the exhaust and will adjust the fuel to create a more efficient burn or optimal burn or a non rich burn. there are other sensors that will help fine tune the amount of fuel that is allowed to pass thru the injectors to create even further optimal burn conditions. MAF mass air flow sensor determines the velocity and thus the amount of air flow thru into the intake manifold and will increase the injector opening time as flow increases. MAP manifold absolute pressure sensor may be used instead of a MAF as as air flows quicker pressure reduces and more fuel will be allowed to pass thru the injectors. All the sensors send info to the ECU electronic control unit to more accurately determine the correct length of time the injector will stay open to give an ideal fuel to air ratio for the most efficient combustion. In a nutshell as I understand it.

09-20-2012, 08:09 AM
maybe someone ,will go further with this reply?

I believe Doc has accomplished this magnificently.

09-20-2012, 08:34 AM
Specifically, a carb is a mechanical device with no electronic control (except for an electric choke in some cases). Any adjustments in fuel metering are made by the user, using a tool (screwdriver, etc) Any other means of fueling that is controled by an electronic means would be EFI. Minor adjustments to fueling are controlled by a computer, the fuel computer is adjusted via an electronic interface.

As explained above, TBI, Multi Port FI, Port FI, and Direct Injection are the most common EFIs. The more complex the system, the better job the computer does in maintaining the proper air/fuel ratio in all situations (temp, humidity, altitude).

09-20-2012, 10:19 AM
The more complex the system, the better job the computer does in maintaining the proper air/fuel ratio in all situations (temp, humidity, altitude).

Well, in theory anyway. But, the more complex the system the more chance of any one aspect failing. Good to keep this in mind.

09-21-2012, 08:48 AM
Good information. Makes sense. Thanks, guys.

09-21-2012, 09:03 AM
Very good information. I find it strange the 07 OB has a Throttle Body on it with injectors. I think Als 07 LSV is like mine and its TPI.

Just to edumacate you a bit more as to why certain terms are used.

TBI - Throttle Body Injection one of the first widley used on cars starting in the late 80s, this was simply accomplished by adding a body above the common carburator and installing injectors. This made fuel economy much better but it was really a facy carburator.

If my computer would work today i could talk about the rest, i just want to be exactly sure before i post the info.

As for it saying Electronic INjection this is due to different types of injections systems. You have manual and hydralic as well. Hydralic was used back in the 70s and early 80s on some cars but its most widley seen in diesels. Even as recent as the Ford 6.0 it was hydralic injection using the engines oil supply at pressures as jhigh as 30K lbs to fire the injector. Most use electronic injectors which are much quiter, this is also one of the reasons the new 6.4 and 6.7 diesels from Ford are so quite.