Carburetor versus Fuel Injected

"I'm buying a new boat &#4

"I'm buying a new boat (20 ft fish and ski) and am trying to decide between a carb versus fuel injected engine - the 5.0L 220HP V8 carburetor engine or the 5.0L 260HP V8 MPI. The boat dealer has told me the carb engine will perform just as well as the MPI and I don't need to spend the extra $2K, but I'm looking for some independent advice. Can anyone help me out? Thanks in advance."

"Part of it depends on how you

"Part of it depends on how you will use the boat- balls out and you'll save some gas. Lots of stop and go or sitting between uses and injected will make starting a lot easier. You are the only one who knows if you really need the extra 40HP or not. If the boat is at the high end of your price range with a carb, go that way. It'll still run fine if you do the required fuel system maintenance but remember to pump it a couple of times before cranking if it sat for more than a day. This way, you won't need to own a starter rebuilding shop.

If you want to use it in California, you'll want to get the injection. CARB is really getting strict about what is used out there and some new boats are coming out with closed loop systems (O2 sensor and catalytic convertors).

Personally, I hate carbs but that's just me. They work. I just don't like to deal with them when they're goofed up, gummed up, vapor locked, loaded with water or any of the other things that can happen to a carb."

"A second opinion. If i had th

"A second opinion. If i had the choice, I would go EFI. Carb will work fine, but you'll enjoy the predictable starting associated with fuel injection. That and how can you turn down 40 more hp?! But then again... $2k will buy a lot of boat gear. Just thoughts."

"The only reason I would buy a

"The only reason I would buy another carbureted boat is the dependability. Hard starting... sometimes, requires a little attention now and then, absolutely.
But carbs are fairly simple contraptions. There's not much that can go wrong with a carb that would keep it from working to some degree... maybe not run all that great, but enough to get back home and critique it at the boat ramp.
I use the boat mainly for off shore fishing... I thought long and hard about what could go wrong, and what I felt comfortable with if I were 20 miles off shore and had a problem.
Ultimately, I'd prefer twin engines, EFI, MPI, whatever. I would also prefer a boat big enough to support such.
In that regard, I'd feel a whole lot more comfortable being off shore in something I couldn't fix as long as there was another, 100% indpendent system to get my butt home.
There's just the matter of an additional $50,000 or so, and all my intensive hand wringing can be for not!
Also, with a carburetor, I think you generally have some indication of a looming problem before it becomes a big problem. I don't have any particular beef with fuel injection. In fact I can't remember ever having any trouble with it in any of the cars I've owned with it. But I think if something were to go wrong with it, it would keep the engine from running at all, and I don't think it would be realistic to think I could troubleshoot and repair it while at sea without carrying a complete spare system."

"As long as the ECM gets RPM i

"As long as the ECM gets RPM indication and there's fuel, an injected motor should run if there's spark and no low oil pressure lockout. It may not be pretty, but an injected motor will run well enough to get you in to shore. Bad MAP sensor or TPS won't cause it to not run and if a relay goes bad, it's easy enough to bypass it."

"good comment. in other words,

"good comment. in other words, most failure modes lead to the system going into "limp" mode where values are assigned to sensors that are out of range and the engine still runs."

"What if the ECM itself dies?

"What if the ECM itself dies? Is it reasonable to carry an onboard spare? Does that happen so infrequently that it's not even worth considering?
With as much trouble as I've had recently with that 2bbl mercarb, I am thinking about converting over to EFI."

"First of all, I would like to

"First of all, I would like to see people stop thinking that "limp" mode will get them around the way it does with a car. "Limp mode" is actually RPM reduction mode, which happens for one main reason- OVERHEAT. If the boat doesn't have a closed cooling system and it overheats, it needs to be shut down so it can cool down to normal operating temperature. The one reason to not shut it down is if someone needs to get out of trouble (big storm, heading toward a waterfall, etc) or if there's a reason to go to shore that makes killing a motor the lesser of two evils.

If a sensor goes bad (MAP, TPS, Knock, MAF), the ECM will show a code and go to the default for that situation and for these sensors, it's not "limp" mode. If the ECT (Engine Coolant Temperature) sensor fails and shows overheat, RPM reduction will happen and it'll run like crap because the ECM alternately disables the injectors in an effort to cool the motor and keep the RPM below 2000."

"Troy- it's really not pra

"Troy- it's really not practical to carry a spare ECM and I haven't seen many go bad. I replaced a few in the 5 years I worked for boat dealers- one lost the IAC function with no visible defects and the others were due to water getting into the main plug, which removed the B+ pin through electrolysis. I have heard of a few others but they rarely go bad. They're also not cheap and need to be calibrated for the specific application. You don't want it programmed for a 21' boat when you have a 34' boat and you don't need the 34' program on a 21' boat.

Converting to EFI isn't cheap, either. Since you mentioned the 2 bbl, I assume your motor is the 4.3L- maybe going to the 4 bbl Weber is a more practical option. You'll also get a little more power without having to spend so much."

"You opened up a can of worms,

"You opened up a can of worms, Wes!

Jeff

PS: I vote for carbs."

"It's actually a 5.7L... w

"It's actually a 5.7L... with that 2bbl it's like running a marathon while breathing through a cocktail straw!
I sure would like to have the ease in starting and the improved economy and more ponnies FI has to offer... maybe next boat, or if I decide to repower when this set-up wears out. I would definately have to spend some time going through the tech manual(s) before I head for blue water!
I don't even recognize some of the terms Jim threw out there.
Either way, I'd probably lean more towards diesel engines anyway... which completely eliminates the carb vs. FI argument!"

"All of the sensors on an EFI

"All of the sensors on an EFI motor are very similar from brand to brand and the GM EFI motors are just truck motors with some changes. The sensors can be bought at any GM car parts department. A manual (if it's a good one) will help for troubleshooting but it won't necessarily tell you how the system works. If you don't know what the sensors do and how the ECM controls them to make the motor run properly, there's a lot of info that you can google."

"don't fight technology. b

"don't fight technology. before long carbs will be obsolete! Can you buy a carborated car or truck?
years from now boat manufactures wont offer carbs anymore either, and people will want FI even more. So If you spend 2k on FI now you will recoop it on the resale. you will also love the reliability! My last boat was 2002 FI, currant boat is 1978 4bbl carb, love the boat miss the fuel injection."