EFI vs Carb.

[jgreen]

I have been told that you can gain about 10mph by changing from EFI to carbs is this correct ?

Is it because you are removing the electronics and no longer have a rev limiter ?

Is this a good option or not ?

I kind of like how the efi works as far as cold engine start up and the safety features of the ecm, but in the quest for more speed, is changing it a good idea ?

What kind of cost might I be looking at and what kind of problems could I run into.

 

[Chris E]

can you reprogram the ecm? That sounds like a helluva lot of work and expense to change all that stuff over. never heard of anyone doing that before. i would figure the efi unit would be faster since it factors in many conditions that a carb engine without a brain can't.

 

[Dave's ZT260]

Once you've had EFI no one wants carbs. Carbs usually produce less power. The only advantage is anyone can jet a carb, but programming the ecm is best left to the pros.

So to answer your question, not a good option.

 

[vinny p.]

Do not get rid of the EFI. You will not gain anything. The only time you should consider going back to a carb is if you are planning on working the motor. Don't fall for the re-mapped ecu scam. It will not help you. It is all b.s. Merc spent alot of time and money getting your fuel curve correct. No one else can make it any better for a stock motor.
I changed motor this winter. I ditched my stock 454 Magnum for a carbed 540. I am still not happy about losing the efi, but I didn't want to mess around with attemting to get the fuel curve correct. In my case, a carb is alot more tunable. I hope I don't regret it.

 

[Dave's ZT260]

Vinny, you’ll be fine. Besides when you add the blower you can add the efi.

 

[vinny p.]

Dave,
No blowers for me.. I never had one, don't know much about them. I think I will be happy with the power I have.
I think I may have said that a time or 2 before, hopefully this time I mean it.

 

[jkeiper]

jgreen:

FORGET IT!! I don't know where you heard that, but it is false information. There are a lot of guys on Scream and Fly running EFIs as fast as any carb. motor. Also the carb motors still have rev. limit built into the switch boxes. (except for some of the older stuff) I wouldn't even think of switching back to a carb. motor.

Jim

 

[jgreen]

Thanks for the input guys!
The EFI is going to stay, I guess the guy I was talking to is going through his motor so it will be apart, and maybe at that point it may be ok to scrap the EFI, and the oil injection and make it a real high rpm motor.

 

[jgreen]

jkeiper:

when the ice goes out this spring, do you have the merc part number for the reeds to put in my motor?

Then if its still ok I will bring the boat down there and we can "wake it up" a little, probobly not enough to keep up with the " <span class="ev_code_RED">SECRET AGENT</span>"

 

[vinny p.]

jgreen,
Sorry but I was referring to I/O type motors. I didn't realize you were talking about outboards. I don't know if what I told you in my previous post pertains to outboards. I never answer any posted question here about them because I have little experience with them.

 

[jgreen]

Vinny, No problem, your knowledge on i/o's is good to read and your advice has helped lots of people.

 

[jkeiper]

Hey jgreen:

Any time after the first week of April should be ok for working on your motor. Have you decided how much your going to do to it? (i.e. reeeds, exhaust tuner, exhaust relief, heads, solid mounts)

If that guy is building a high RPM motor, he'll have a lot more to worry about than the EFI rev. limiter. Yuo can't run the stock cast pistons and the porting should be changed to take advantage of the ultra high RPM. Oh yeah, how bout the flywheel and the rotating assy should be balanced.

Jim

 

[jgreen]

Jim;

I want to do the reeds and the tuner for sure, solid mounts if they would really benefiet me, and anything else that is not really involved, maybe we can throw some guages in it then to, temp., water pressure, any other quick things we can do to help it out.

 

[Tweed]

Converting to a carb from EFI? IMO, you made the right choice not doing so.
Carbs meter fuel from an airflow signal through the venturies/boosters. Thats it; Carbs mechanically responds to an airflow, and can be dialed in very well at specific throttle settings and make great power. For example, Carbs can be set up w/ a killer A/F ratio at WOT. In fact if all you plan on doing is WOT = Racing, you can equal or exceed on EFI unit. But who runs @ one throttle setting? For Joe Boater, all around performance is what counts. Carbs cannot even be compared to a EFI systems ability to deliver precise fuel and ignition requirements at many different throttle settings and load demands place on the engine. Carbs are a wet flow system with inherent problems associated with fuel suspension and dropout as the mixture travels through the intake tract. Another reason why all the new direct injection EFI's are superior to the old, let alone carbs.
Aint technology great? Only one teeny prolem that rarely, albeit infrequently appears. When the EFI acts up, good luck fixing it w/ "excellent mechanical aptitude" that used to work w/ old school technology. Stuck floats and leaky gaskets is one thing to fix; the other technology requires a whole different set of tools that are won't be found it that tool kit underneath your boats back seat. FWIW