Carb vs Fuel Inj?
 

What are your thoughts ? looking for the best of everything [ naturally ] the best performance with reliability, restarts when hot, docking?
thanks RB

aftermarket fuel injection...something that is tunable without sending ECM out

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The BEST? Call Young or Boos.

Efi ftw

+1 agree

My thoughts stay away from efi that isn't smart enough to tune itself. With that said a good Carb is still very hard to beat.

If i had a 600hp or less carb'd setup, i'd install full dry with mufflers and a Holley Terminator EFI. Nothing wrong with properly setup carbs though.

https://www.holley.com/products/fuel.../parts/550-405

I was just thinking that the MPI would be a lot less trouble on a boat. Just your basic stock Merc MPI on a stock motor or a stock carb on a stock motor. I am looking to buy a boat and have stayed away from boats with carbs. I am looking for something that is reliable, that idles good, and restarts are no problem after a hard run. Will a carb do all that no problem? I am sure the carbs are a lot better now than when I was messing with hot rods many years ago!
thanks RB

do a search about the mpi problems and vst tank,you might reconsider the reliability of some efi units.

A carburetor will do all that and not quit working.
Nowdays people think carbs are junk and EFI is a god,not the case.

After just a quick search it seems most of the problems were with the EFI when they first came out, is this true that maybe after about 1999 they seem to have less problems?
thanks RB

nope....like said before, search vapor lock, sooted transom....

Old early Merc EFI systems were a decade or more behind in technology WHEN THEY WERE NEW! The old factory systems can't hold a candle to the new aftermarket systems. I love my Holley HP EFI self tuning system. Set it up correctly with a return regulator and it will never vapor lock. The old Merc systems used a single large fuel rail that were returnless and just would bake on top of the motor from the latent heat when you shut them off. You can get good aftermarket systems for about the price some people think their take off Merc systems are worth.

modify the merc system to return to the tank and most problems are solved.

It is a trade off. EFI more reliable but when it needs attention it is a nightmare with dozens of sensors/etc that could be causing trouble. 10% more power. A carb and one wire distributor is nice, nothing is simpler, you can draw the entire fuel and electrical system from memory in seconds. EFI is wildly more complex.

Carbs have made more power in every comparison i've seen. The one benefit to EFI I've seen is that it can tame larger cams and help them idle at lower speeds.

no warm up.I start and go at the dock.

[QUOTE=hogie roll;4245871]Carbs have made more power in every comparison i've seen.
:bsflag:
With injectors above stacks?

The stock mpi worked fine on my ProCharged 502. It did have a return to tank fuel line setup. That said it always fired right up. With my new build this winter I'm upgrading to the Holley HP EFI but ide keep the old mpi long before ide run a carb. This is an expensive boat though, if I had a small "hot rod" jet boat then a carb might be OK.. Just my opinions.

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It seems to me there is no easy answer some like em, some don't. How about we look at it this way if I found a boat that was everything that I thought I needed but it had carbs on it would you not buy a boat just because it had carbs? Or on the other hand would you not buy a boat just because it was F.I. ?
Thanks RB

Didn't really matter for me,except if it was EFI it would of been 500 blue motor.Wound up with carbs and a blue motor they are great.

I would buy either one.

I have a carb and I've done EFI. In the long run the carb has fewer parts and will require less service. On a stock cam motor it is hard to tell the difference between the 2. The new HP Holleys are really tunable you just have to know how to do it. I have a fairly radical cam and I'm running a carb, for the most part it's flawless, I can idle for an hour, get to open water and tromp on it. It's real weak point is trying to maneuver at idle in strong cross winds or currents. It has to idle at 950 rpm to get it to 600 in gear and with a big cam, it's loping pretty good. For me even self tuning is out, because they need 9 inches of vacuum in gear to learn the idle. I'm looking at the FAST EZ-EFI 2.0 for my next motor. It has the benefits of a carb in that you are introducing the fuel upstream to cool the charge and improve fuel atomization. But I can't use the self learn function, I have to do an open loop system. I don't know about anyone else but dumping a bunch of fuel on the backside of the intake and hoping the inrush of air will provide even fuel distribution and atomization doesn't sound optimal. I know it works, it's just when you are looking for every last hp, I look for other solutions. I have seen dyno tests with Fast EZ_EFI 2.0 and it out performed a Holley HP. That is the only time I have seen and EFI system produce more horsepower than a Carb. Cold running and idle is certainly better than a carb and for a lot of people that's worth it. You can also get a lot tighter control on your AFR with EFI. I put an Edelbrock EFI system on a small block Chevy with a Victor Jr intake and everything improved over the stock carb and dual plane intake. The best part I was able to lean out the cruise and add timing to improve fuel economy by 50%. I would do a search on EFI for Everyone, there is a lot of good information there.

The cooling effect the carb provides won't be realized with fuel injection no matter where the fuel is introduced. I think efi systems preheat the fuel to much, or the fuel isn't undergoing phase change in the same location. It's a bit of a mystery, as I've never seen a test where they tried to control IAT on an EFI system by cooling the fuel somehow. Now that would be interesting.

I have not seen a carb vs injection comparo with injectors above stacks. But on normal intakes and tunnel rams the carbs have made more in the comparos I've seen.

why do you think a carb has cooling ? fuel bowls sitting on top of the engine...EFI fuel strait from tank...with return system fuel is going to be much cooler than fuel passing thru carb...

There is a lot of good info here!
Thanks guys
RB

The cooling effect takes place when the fuel goes from liquid to vapor. I believe Super Chevy or Engine Masters did a comparison between the Fast EZ-EFI 2 throttle body and an HP Holley, the Fast EFI actually produced more horsepower than the Carb did. It's the first comparison of this type I've seen.

M50---if the motors have nothing, consider spending the extra bucks and go EFI. Generally starts better, a little better mileage (but you have a boat....nuf said) seems less prone to bad fuel/storage. There are some really good threads on some of the self learning systems here.

I firmly believe that well setup carbs in the marine environment provide more bang for the buck than EFI, so if the boat HAS carbs, I would leave them and enjoy OR, if motors have nothing, and price is a consideration, carbs (particularly on a twins) is a lot less expensive to acquire and setup. With carbs, spend an hour or two setting them up, and if you never raised the hatch again, you'd be hard pressed to know the difference. I've had both, build both, still run both, and I like them both.

A lot of talk goes on about the theory of carbs/EFI and what you see on a dyno. I've spent hours over dynos, and thousands of hours in boats, and if I'm at the lake, in the sunshine, my beautiful family and friends by my side sipping a cold one, 12.6 AFR vs. 13.1 AFR is pretty much meaningless. Set either up right and go to the lake and enjoy what ya got!!!