Carbs vs FI... Pros/cons
 

Everyone has an opinion on this carbs or FI. So, any input would be great. What do you think? Pros/cons? In salt water environment. Use carb and higher HP lower price OR spend more get FI.... Which one is more reliable in your opinion?

carbs are more reliable, they make the same hp as efi, just make a little less tq... and are an azz load of cash less costly

Carbs suck in rough water. Good fuel injection is absolutely the way to go IMHO

Not necessarily a HP advantage either way, however FI is more likely to be drive-able with easier shifting.

if the carb is set up properly you will have no issue in rough water, it is like setting up a carb for a car that corners hard, jet extensions, overflow extensions and you will have zero issue is big water, trust me i know...rm

My last 2 motors since 99 have been EFI. The latest re-do on a 509 was going to be EFI. My motor builder who always seems on top of current trends and is a performance boater, is now trying to talk me into a carb!?!! He promises I will be "so much happier". According to him, a boat is the perfect application for a carb (for most people); somewhat constant temps with similar humidity, as in summer sport, constant elevation as in same lake. I am promised same idle and smoothness, same max torque and a significant bump in horsepower. Put your hand on the intake, feel the cold, there is your answer. Of course this entails him building a custom carb/intake combo, but still the price is cheaper than just upgrading my current EFI. It sounds so simple: just pull the carb at the end of the season and store dry. Not sure what I'm going to do yet, but I am VERY sure that a carb is more reliable than even a factory EFI. Almost everytime I have had issues in the past it has been EFI related.

Liquid lounge/ratman...I am hearing the same from engine folks. The thinking seems backwards, that's why I threw this out to see what offshore people think.... Can't get a car w/o FI today, so why not same for boats? I'm most interested in the HP gain and price difference... But concern over a carb not being adjusted right and flooding or burning a piston.... All those things that used to happen to me when FI was a dream.... Thanks for feedback

I have had two stage v racing carbs built by Dean Nickerson . You would swear my engines were fuel injected by the way they fire and run . Never a problem in rough water and both engines run very crisp . I run Marvel Mystery Oil through the carb at the end of the season and let it on the engine . I never drain it as I have seen too many problems caused by dried out shrunken gaskets and ruined accelerator pumps . Dean is pretty close to you , give him a call .

M y next boat I want it FI. On the other hand, the one time I had a carb running rich, I fixed it myself, with a screwdriver! When FI goes south, you need a computer and usually a sensor to solve the problem, which I don't have... Tough call I guess

i run carbs on my 8.3L whipplecharged engines,but i am thinking about going to efi.a good efi system compensates for humidity,altitude&temp.there is a reason all newer cars and almost all newer boats have efi.as far as power,i dont see any measureable difference from one to the other.imo,the determining factor in choosing is price.

The blower engine in my Eliminator was FI, stock merc modified with a whipple side mount, no problems at all just cracked the block. I am building a new blower engine also whippled FI. My Baja was stock 454 mpi, no problems either. My Kachina got new carbed 650hp 540s this year, spent the summer dialing in & running it ragged, no problems with fuel system at all. The only difference I could see was having to pump the throttle a couple of times when first started. I would have to agree if the carb is set up correctly it will be fine. Randy

I've had both Carbs and EFI. Both have their plus's and minus's.
I've had carb engines flood the fuel bowls when lauching the bow high and pulling back on the sticks.
I've had some minor vapor lock issues with my MPI's in exteme hot humid weather.


I thought most of the marine EFI set ups used fixed curves for fuel mapping and do not self adjust because of the lack of O2 sensors????

I had one engine builder tell me that one of the main reasons for the marine industry switching to FI was due to emission standards, along the same lines that catalytic converters added to new marine engines.... Other than that he claims carb better than FI since maint and repairs easier....

I think its really a tough comparison to say which is ''better". Theres a lot of different EFI systems, and different carbs.

Hands down carbs are much cheaper. Carbs today are much better than they were 15,20, 30 years ago. Once you figure them out, tuning them is easy. And you can install 02 sensors, which really helps for an efficient tune. Years ago, all we could monitor was spark plugs. Today, with 02 sensors, you can fine tune your engines from idle, to wot. You can eliminate that "pig rich cruise", or "lean wot meltdown" etc. Basically you can fix holes in the fuel curve easier. Fuel system is pretty basic, a mechanical pump and a decent size fuel line is usually all that's needed.

EFI, has some great systems out there. A port injection will deliver outstanding fuel distribution, much cleaner idle, etc. Throttle body injection is nice, but if I were to make the jump to efi, I'd really like to go with port injection.

I think its more of a personal preference, and budget oriented, on which system is best. Both can work really well. Generally speaking, there isn't much "power" to be gained one way or the other. The one thing I have always loved about carbs, is generally, parts are super cheap, and can be fixed at the dock with a quick trip to autozone should you have a gasket leak, power valve blow, or needle seat mess up. With EFI, you might be down until parts get shipped to you should something fail.

If question is carbs vs a total ecu system there is no question. With a good ecu like merc 1075 there is no comparison. No way you can make the consistent hp with the longevity with just carbs. Good computers will take so much info a maximize power through all rpm. Some computers can read each cylinder and sense detonation, and it will pull timing out of each individual cylinder. It reads so much info its crazy. But I do agree that carbs up to 1000 hp are a great way to go, you are not stuck with all the tune up guys, plus there are so many sensors on a ecu motor to go bad it can make you nuts.

Really is a toss up, but if your filters clog up with an efi system and your pressure drops it could equal meltdown. A lot harder in my opinion to melt a carb'd motor once its dialed in. As stated earlier both have there pro's and con's. I for one and am not 100% locked on either.

Properly setup EFI engines should always out perform carbs in the long run, especially when talking about blowers motors. With carbs your pumping liquid thru a compressor designed to move air. Sequential port injection is way more efficient here.

As Mild Thunder touched on the biggest carb risks above, I had this same conversation with a friend some years ago while driving home with his two 1300hp Cobra engines that were properly dyno tuned, twin dominators on top PSI's. Once installed in the boat, those fresh engines only made it 10 minutes before melting the heads down. Seems they didn't like being starved for fuel when he forgot to switch on the electric boost pumps. I wasn't around to see it happen, but heard the result was a violent 120mph spin out when that first one seized up..

Had those been EFI with O2 and knock sensors, she would have automatically pulled timing if the ECU detected it going lean and detonation started. As someone else listed above, the popular open loop EFI setup from Merc used for years isn't the best option out there today. With the new wide band O2 sensors and closed loop setups, there is no reason modern EFI shouldn't out perform carbs at any HP level. It's just finding an engine builder who understands EFI tuning, and that's not always easy to do when your talking marine engines.

griff,you are correct but the newer stuff does use a o2 senser,even the lower performance merc packages are useing them and the better aftermarket ones like the holley dominator and the megasquirt units also incorporate o2 sensors.

one thing to keep in mind,when you put fuel in the airstream above the rotors you do two things,cool the supercharger and help seal the rotors in a roots or screw supercharger.

Here's the problem with this comparison, fi can range from very basic to extravagant, many benefits to a top notch injection systems.

As far as the carbs pumping liquid through the blower, I cant say I agree that, that ''hurts'' efficiency. The fuel has been known to help cool the air charge, and reduce internal heat inside the compressor, at least on a roots blower. This is one of the reasons Roger at C&S carbs, will put his carbs up against any port injected blow through setup, HP wise. Especially with the ''aerosol design". Not to say the carb is better, because I would much rather have EFI on a blow thru setup. Even on a roots blower, Id love EFI, but its honestly not in my budget to put together the proper system, that in my opinion, will be worth the added expense to convert.

As far as the carb'd psi blown deal melting down, well sure, starve it for fuel and its over in seconds. A simple set of fuel psi gauges, or low fuel psi switch with a warning light would probably saved those engines. . Fuel system issues in any engine will lead to melting parts. But, like you said, not all EFI systems are created equal. Something more modern, with 02's, knock sensors, etc, will be much better than some of the primitive injection systems, like merc offered not long ago. To take full advantage of the benefits, you really need to build in the safety factors into the system.

I really like EFI, but it has to be the right setup. Just because its ''electronically controlled" doesn't mean anything to me. A late 80's GM TBI injection is "electronically controlled'', but it still sucked. It really offered nothing over its carb'd predecessor other than you can start the engine without pumping the accelerator.

I have friends who aren't very engine knowledgeable in general, that are boat shopping. They have the impression that, as long as its ''EFI", its reliable, safe, and will offer trouble free boating. And if its carb'ed, its gonna be unfriendly around the docks, require constant tuning, and use more fuel. that just always isn't the case.

Take cost out the equation and the choice becomes clear. EFI wins everytime the only reason for carbs is cost plain and simple.(or rules if you are racing in class, but again thats to control cost) New EFI systems, like Holley, Fast ect. are not hard to use, they just cost more.

I pretty much agree. How much for a carb and a mechanical fuel pump? And how much for a ready to run EFI system like a Holley or FAST?

I the reasons carbs have been used so much is cost based, simplicity, and generally they just work. If price wasn't a concern, without a doubt I'd have injection. But, I'm on a budget, want to go fast, can't afford blowers AND efi. Like the old saying, "INJECTION IS NICE BUT I'D RATHER BE BLOWN".

If you can have both its a win!

My carbs @ 925hp run like an EFI engine or better. Its all about who is tuning them.

Agree. Mike Tkach on here has a pair of 588s with 8.3L whipples, and a pair of 1050 quick fuel carbs. They make 1200HP, and idle at 650 in gear. The bypass valve in the whipple is nice.

One nice thing about EFI though, it can be a big help for some of the guys running radical cams, combined with 18'' six blade props. A lot of times in order to get a carb'd setup not to fall on its face when shifted with big props, you really need to give them a lot of fuel and air. Which then becomes a problem of a fast neutral idle speed, or a rolling idle(surging), in order for them not to stall. Some builders have fought this problem, by adding shift solenoids, so that the throttle lever will be bumped up when put into gear. This eliminates that 1200RPM Nuetral, 700 in gear scenario when setup right. With EFI, the controller can take care of that.

My experience with those older TBI style setups, Holley or FASS, you could give it to me and I'd probably still trade for a good carb...

However one can easily hit the local bone yard and scavenge everything ya need to convert any marine engine to modern EFI for a little bit of nothing. With all the aftermarket ECM tuning options available today, I'd opt to build my own setups. Browse one of the LS forums and you'll find everything ya wanted to know about swaps. Big cams, blowers, turbos, all purr like a kitten when topped with modern fuel injection..

yep and what makes me laugh is the person that has no phuckin idea on how all this stuff works try's to drive through it instead of parking it and blames their phuck up on the guy that worked on his $hit last..

joe,efi can be reasonable if you know the rite people and you do know the rite people,,just have to ask!

Dean Nickerson for the win! That guys knows blower carbs VERY well! And does phenomenal work!

so you buddy wasn't running EGT temp sensors? i know i would on an engine set up like that...rm

i disagree, usually carb engines will make more peak hp than most efi systems in a n/a set up. a carb will make a little less tq and the carb eng tq will be a bit higher in the rpm range.

on max effort blower engines i think, that is where efi shines... rm

blower surge is cool as hell... rm

Aside from being able to adjust and optimize your fuel curve for every load and rpm point, the biggest benefit to using a good efi system is that it manages the whole engine. You can program it to monitor every conceivable sensor and engine condition, and then tell it what you want it to do when a parameter is out of range; pull timing, reduce rpm, add fuel, etc. Total engine control, built in wide band control and monitoring, guardian system, knock protection, built in data logging, etc. really make the extra cost up front worth it. A good efi system is far more reliable then any carburetor, and will last much longer. Also, if you value your time, tuning an efi engine's fuel curve takes a fraction of the time it takes to dial in a carburetor throughout the whole rpm range.

I can attest to that. Dialing the fuel curve in on a carb setup IN the boat, is time consuming. There's more to it then just jet sizes. esp with twin carbs on twin engines.

I wanna say a while back I priced out a EFI system for a blown roots setup, and it was around 5k per engine? Does that sound in the ballpark?

Was my first question also Ratman.... Wasn't involved with the rigging, but it was all top class, so could only speculate why no safety.

I personally run an EGT gauge, sometimes I take a peak at it....

http://www.altfuelsgroup.org/picture...one-%20114.jpg

You can do it a lot cheaper then that. Assuming you've already got an adequate fuel system, you could easily modify your carb adapters for injectors. A universal retrofit kit comes with a 1000cfm throttle body, ecu, wiring harness, fuel rails, weld in bungs, regulator, wide band, and all sensors for $1900. A second throttle body is $500, and a set of injectors is $300. $2700 total.
Or you could go with two throttle body injection units for a bit cheaper if you just want a bolt on option.

as stated before... The ONLY reason for a carb setup is the cost and/or the lack of knowledge by the owner or builder of an EFI setup. You don't see a carb on anything from Mercury. You also can't go to any car lot anywhere and find a carburetor of any kind. Technology is better if you have the knowledge to install and tune.

Yes there are some builders out there that can dial in a carb. It is also true that just about anyone can dial in an EFI closed loop system with a laptop if in fact it does not tune itself.

MAP sensors to adjust for altitude, etc and switch to different fixed curves even without O2 sensor input.

Perfectly said...

You read my mind. The problem is that most boat factory FI are still stone age compared to automobiles so most of the nice FI boat setups are aftermarket ($$$). Being able to adjust fuel and timing curves thru the entire rpm range is far superior to what you can do with carbs, HANDS DOWN. I've built more LS drag motors than I can count and I'll never go back to carbs. Nothing like getting invited to Pump Gas Drags and having a car drive like stock in traffic while listening to the radio while carb'd competitors are loading up, stalling, & dying lol

As far as the original posters question, it's very easy to answer what the general boating community think is superior in the carb vs FI debate...

Look at prices for used 700SCI's and 1075SCI's versus used 700hp and 1100hp aftermarket carb's blower motors. You'll immediately notice which demand a higher resale value.

Ok,

If I want to convert my Sterling carbureted 1100s (that ran flawlessly last summer, never lurched or died around the docks, and started every time I hit ignition) to EFI, what would I need to do?

They are currently at Native getting rebuilt and the boat is at Nauti Marine so now would be a good time if is truly worth it.