efi vs carb?

if you are feeling better with a carb just go for it , a good one will get the job done .

that will not change the fact the best carb will not compete with a mpi . i had both and would never return to a carb .
 
I haven't run efi in marine applications but have had good luck with 3 different boats with the 5.7 and Edelbrock combination. During the couple thousand hours logged with them, the only problem I had was a choke wire falling off on one of them which caused it to run noticeably rich at lower rpm's and hard start warm. With a boat running at sea level all the time, what do you guys think the true gain would be in economy on say a 7000 lb boat with efi? I run about 10 gph now at a 3200 rpm cruise.
The first Edelbrock I had was in a 20' jet boat. It was used at all elevations up to 3000'. At the highest elevation it still ran like a champ but did lose close to 300 rpm at WOT. Would that not be the same for an efi fuel system? Thought it was more of an atmospheric pressure thing.
 
We seem to be overthinking this EFI vs. carb thing. Technologies change over time and the changes improve things in many cases. EFI improves starting, smooths out idle, increases throttle response, improves mileage and reduces emissions. So it's just plain better than carbs. But I would never buy a boat on the basis of whether it has EFI or carburetors. They are different approaches to the problem of combusting fuel. Both work, one better than the other. Hull shapes and amenities effect your boating experience much more than a properly functioning fuel system whether it is fuel injected or carburated.
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[QUOTE="EFI improves starting, smooths out idle, increases throttle response, improves mileage and reduces emissions.
This is just flat out bad information. There's 124,000 btu's in a gallon of gas, The same amount of energy is produced whether efi or carb so mileage will be the same. Smooth idle, increased throttle response, instant starts, is all about who set your carb up if that's your problem. Should not be blaming your carb if this is happening.
 
My Quadrajets have been on the boat for 10 summers since I rebuilt them when I bought the boat. At the time I added electric choke conversions. To this day they have run flawless and start within 3-4 revolutions of turning the key. I prefer the engine crank a few revolutions anyway as it gives the engine a few seconds to build oil pressure prior to firing off. Besides I like simple stuff that I can fix no matter where I am.
 
I truly believe one of the big drivers for efi was emissions.

I go back to Harley’s only because they’re so easy to work on for me because the engine is so accessible.

All the efi Harley’s require O2 sensors and run extremely hot. So hot a favorite mod is to install an oversized oil pan w inlet and outlet lines on opposite ends of the oil pan vs right next to each other.

I haven’t been in an efi mercruiser engine well but if these require the same emissions standards I know they’re running muy caliente.

But I won’t buy a boat because of having or not. I just know I don’t work on that fancy stuff. :confused:
 
El Capitan said:
I truly believe one of the big drivers for efi was emissions.

I go back to Harley’s only because they’re so easy to work on for me because the engine is so accessible.

All the efi Harley’s require O2 sensors and run extremely hot. So hot a favorite mod is to install an oversized oil pan w inlet and outlet lines on opposite ends of the oil pan vs right next to each other.

I haven’t been in an efi mercruiser engine well but if these require the same emissions standards I know they’re running muy caliente.

But I won’t buy a boat because of having or not. I just know I don’t work on that fancy stuff. :confused:
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The Harleys run hot because to meet emissions HD is running them as lean as they can to comply with emission standards, take your bike out and get a good person to dyno tune it and you will see a big difference in performance and how hot it runs but you might want to change the cam in it to really take advantage of the tune. Had both of mine dyno tuned and it does make a difference with heat.
 
I've had both, Carbs that are well maintained (this is key) can be great and dependable. I had MPI on a 2007 90 HP 4 Stroke that was flawless. Easy quick starts with no choke or pumping and steady at all speeds.
 
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atrick said:
The Harleys run hot because to meet emissions HD is running them as lean as they can to comply with emission standards, take your bike out and get a good person to dyno tune it and you will see a big difference in performance and how hot it runs but you might want to change the cam in it to really take advantage of the tune. Had both of mine dyno tuned and it does make a difference with heat.
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This is my bitch, sans efi.
 
scoflaw said:
[QUOTE="EFI improves starting, smooths out idle, increases throttle response, improves mileage and reduces emissions.
This is just flat out bad information. There's 124,000 btu's in a gallon of gas, The same amount of energy is produced whether efi or carb so mileage will be the same. Smooth idle, increased throttle response, instant starts, is all about who set your carb up if that's your problem. Should not be blaming your carb if this is happening.
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Sorry but if carbs were all that great they would still be the norm. Yours is a minority opinion based upon emotion not facts.
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sbw1 said:
Sorry but if carbs were all that great they would still be the norm. Yours is a minority opinion based upon emotion not facts.
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Emotions? Funny guy, you don't get around much do you? Visit other sites? What part of my explanation sound emotional to you? I do know you hate to be wrong LOL. Do some research please. When's the last time you owned a V8 with a carb? Grumpy old guy that's always right, yah we got a few here. Ha Ha
 
well ... electronic fuel injection generally aims to deliver the correct fuel to air mixture at any running condition for optimum combustion .

this is a cold vs a hot engine , this is no wake speed vs wot , different air temperstures , different air density (elevation) . a carb as a mechanical device cannot adjust to all these changing conditions and so delivers an average good but not optimum fuel/air mixture at the expected operating range .

due to better combustion and so better use of the energy inside the fuel less fuel is needed for a given power or the engine delivers more power at a given amount of fuel - better mileage .

response is better when you "gun the engine" since the fuel injected under pressure is of course quicker at delivery than sucked in via the carb , especially at a multi port injection.

further benefits are improved emmisions due to more efficient combustion and an electronic idle stabilization where an efi idles in or out gear the same as well no choke or prime is needed since the electronics will adapt to a cold start.

there are decent carbed boats who perform fine and you are happy but a carb never can react to changing ambient and running conditions like an efi , this is like asking if a mechanical calculator is better than a computer or if a diesel with a mechanical fuel pump is better than a common rail.
 
You have a point with the air density "elevation point", but the average joe who runs his boat at a particular elevation and at a certain time of year doesn't have a problem with a carb. Granted a vehicle that's used daily and sees temp swings from 0 to a 100 will benefit from EFI.
 
Not to hijack this thread :rolleyes:

Is the injection direct into cylinder or before the valves?

I want nothing to do w direct injection on boat, truck, nor my lawn mower.

See Ford trucks w DI. Most guys are having to install catch-cans. I’ve seen what builds up on the back of the valves. It’s like lava that’s cooled and hardened.

I’m headed to look at a 1996 mercruiser 454/300hp I believe it’s efi.

Does anyone know if theses are DI?
 
its not direct injection .

afaik the 'efi' was the first generation with one nozzle for all cylinders on the manifold while 'mpi' has a nozzle for every cylinder directly before the intake valve so mpi is far superior to efi .

your sooted intake has nothing to do with fuel injection but with exhaust gas recirculating systems where a part of the exhaust gas is provided for another combustion to reduce emmisions .

boat engine does not have egr
 
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I wouldn't say far superior. The first efi's were like electric carbs. 2 throttle bodies on top of the manifold.

What was so wrong with them? The vacuum got the fuel to the needy cylinders. Much like a carb
 
aerobat77 said:
its not direct injection .

afaik the 'efi' was the first generation with one nozzle for all cylinders on the manifold while 'mpi' has a nozzle for every cylinder directly before the intake valve so mpi is far superior to efi .

your sooted intake has nothing to do with fuel injection but with exhaust gas recirculating systems where a part of the exhaust gas is provided for another combustion to reduce emmisions .

boat engine does not have egr
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Agree and disagree. The traditional intake fuel injection washed the back of the valves w gasoline and soot was combusted in the cylinder when the valves opened.

I’m happy to learn there is no DI in boats. Whew.

Thanks for the education on efi guys.
 
Even the mpi's are batch fired. 4 go off then the other 4, so not that efficient. Fuel is hanging around until it can be used,
 
well ... mpi provides fuel under high pressure to every cylinder directly before the intake valve where efi provides fuel to the manifold .

the fuel delivery ( engine response ) is on an mpi quicker due to shorter travel and atomization is better ( more power) . a mpi sucks pure air thru the manifold - no mixture .

i think the ecm is also more powerful in calculations/second .
 
scoflaw said:
Even the mpi's are batch fired. 4 go off then the other 4, so not that efficient. Fuel is hanging around until it can be used,
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you are correct - the next step would be a true sequential injection where every nozzle fires in accordance to the cylinder cycle .

@El Capitan : yes , direct fuel injection produces more soot at all , egr does the rest of the mess . the marine engines we are talking here do not have this problem
 
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