efi vs carb?

El Capitan

El Capitan

Well-Known Member
Jul 9, 2014
3,829
Chicago IL./Vero Beach, Fl
Boat Info
1970 SRV 180 w 2.5L Mercruiser.
2000 Ford Expedition Eddie Bauer
Engines
120HP Mercruiser
Thinking about taking a look at a SR from original owner 1986 SRV210 he repowered w factory mercruiser 5.7/350hp efi and new Alpha drive. Transom and aft stringers redone at same time.

Question about efi. How are these in terms of reliability and maintenance vs good ole carb?

My mechanical skills are limited to fuel, air, spark.

EFI in a marine application gives me the hibbie jibbies.
 
I'm not sure it is worth it unless you have 5.7 efi lying around to use. I started to head down this path several years ago thinking that replacing the Holley 800 cfm carbs I have with Holley Sniper EFI units would be a good idea for fuel savings.

EFI's rely on a wideband O2 sensor to adjust fuel trim which should make them more efficient. So as a first step (with the carbs in place) I installed wideband O2 sensors on each engine tied to a set of gauges on the helm. What I discovered was the primary circuit pulsed 14.7 afr (air fuel ratio) with 72 jets and the secondary system ran way rich at 12.8 afr with 92 jets (wasting gas). A simple jet change (82) on the secondaries brought the afr from 14.4 to 14.7 across the throttle range under load.

At that point....I didn't see any advantage to taking the next step to EFI since it was unlikely that I would see any fuel improvement at no wake or cruise speed.

Buying the O2 sensors, riser plate and wiring them in cost about $200 per engine which will pay for itself based on reduced gas consumption. I'm not sure that dropping $2,000 to efi each engine would ever pay back from the tuned carb version I have today.
 
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I have owned both and EFI is absolutely reliable. The biggest change you are likely to notice is in starting. You just turn the keys and the engines fire right up. My carburated engines were also absolutely reliable, but to start them required a pump or two, before they would catch. Sometimes took two tries. Once they settled down, excellent performance. EFI is newer technology and you would expect to see improvements. I believe fuel economy was better as well although I never worried too much about mileage. After all it's a boat we're talking about. I would make sure the seller had a knowledgeable mechanic doing the work. If that is the case and no corners were cut, it should be fine.
 
Yup. I have zero concerns about fuel consumption for my application.

I have a 1970 Harley. Carbed obviously. My riding bros all ride efi Harley’s w O2 sensors. They run extremely hot, and lean. Such that Harley sells a heat shield for your balls. It attaches between the pipes and the seat.

I just want simple and reliable.
 
I had a 1998 Volvo Penta 5.7 GSi (EFI) in a 24 foot cuddy cabin for 14 years. Extremely reliable and only 6 gph at 3000 rpm.
 
I have owned 3 boats with carbs and 3 or 4 cars wiht carbs. I like the fact that I can rebuild the carbs if needed and it simplifies any problem solving. However, it was only my first boat where I have ever had to do any carb work. So in about 25 years of boating, one carb rebuild and it was a bad float on my first boat 20 years ago. I would not decide on a boat based on carbs vs EFI.
 
EFI has been around in boats for a long time. It's very reliable. If you like dinking around with the carbs it's not a problem. EFI just simplifies the operation and reliability of the boat.

The only problem I had with my EFI engine in 12 years of ownership was clogged injectors from the Cool Fuel module flaking paint. Fixed the cool fuel module, have the injectors cleaned, and good to go. I see that as not so much an EFI issue. The engine simply started when I turned the key.

By comparison I had a carbed Mercruiser engine a 1990 Larson. It often was finicky to start, and lots of times stalled when approaching the dock. I also needed to rebuild my outboard carburetor at least every 2 years and often more often. When tuned right it ran great - but it was a lot of effort to get dialed in and by the end of the season it often needed to be tuned again. I just sold that outboard and got a new EFI model so I can just enjoy the boat.
 
I work on both. Any marine mechanic will tell you they make a lot more money working on EFI systems because of the number of things that can go wrong and the cost of the parts. One Cool Fuel incident will easily set you back a few boat bucks.

I don't disagree that carbs require attention but they are far simpler to diagnose and maintain.

My main point is that a properly maintained carb will match an EFI system for performance. If the only differentiator is turn key starting.....then put a marine grade electric fuel pump on it instead of the mechanical pump and enjoy turn key starting.

Personally....I like both for different reasons.
 
Dang. There’s a boat I’m interested in was recently repowered w mercruiser 350/300hp efi plus new Alpha drive w transom and stringers redone.

I new this efi thing wasn’t a simple issue for me. I really prefer simplicity and reliability over high performance and efficiency.
 
I've had both and agree with much of what the others have said. EFI is preferable for me. One thing I found with carbs is that the ER would often have a gassy smell shortly after shutting down the engines. It may have been the gas left in the carb evaporating and coming out of the breather. This is never an issue with EFI. Starting is easy (car like) and I never worry about the engines stalling if I decide to leave the dock without letting the engines warm up.
 
to be serious of course a fuel injected engine beats a carb in every situation - turn key cold or hot starting , stable idle , no stalling , better mileage , no problems at 'hot and high' conditions and much more .

the answer to the question is obvious
 
PlayDate said:
I work on both. Any marine mechanic will tell you they make a lot more money working on EFI systems because of the number of things that can go wrong and the cost of the parts. One Cool Fuel incident will easily set you back a few boat bucks.

I don't disagree that carbs require attention but they are far simpler to diagnose and maintain.

My main point is that a properly maintained carb will match an EFI system for performance. If the only differentiator is turn key starting.....then put a marine grade electric fuel pump on it instead of the mechanical pump and enjoy turn key starting.

Personally....I like both for different reasons.
Click to expand...

The best carburetor I ever tinkered with and just love are the SU carbs. Got one on my Harley and the dang thing is so responsive and maintenance free.

If I can find a freaking boat in this market for my application it won't matter if efi or carb at this point.

This boat market (and RV, motorcycle, camper) is nuts!
 
El Capitan said:
The best carburetor I ever tinkered with and just love are the SU carbs. Got one on my Harley and the dang thing is so responsive and maintenance free.

If I can find a freaking boat in this market for my application it won't matter if efi or carb at this point.

This boat market (and RV, motorcycle, camper) is nuts!
Click to expand...
Try getting a pool built!
 
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