MPI to Carb ??
 

Hello all ,I have a 98 502 mpi has anyone changed over to a carb system and whats are the pro's and con's .Thanks alec

Re: MPI to Carb ??
 

Why are you switching over do you have a problem??

Re: MPI to Carb ??
 

I also have to ask why?

Re: MPI to Carb ??
 

There are no cons, except that you won't have "turn key" starting. You might have to pump the throttle a couple times before you start it. If the carb is set up correctly, except for when its cold you won't know if it has efi or carb.

The benefits are that if you are planning on building that motor for more HP, that you can do it cheaper/easier with the carb/no computer controls.

Re: MPI to Carb ??
 

I'm by far no fuel engineer, but it seems to me that a fuel vapor would be easier to ignite than droplets squirted into the intake.

But I have the feeling it's probably so he doesn't have to be at the mercy of a shop to tune his engine.

Re: MPI to Carb ??
 

alecsammy, I can sympathize with your desire to consider a carb. I have EFI's and one is problematic. No one can seem to find the problem. Mine have been great for many hours but the lingering problem sometimes makes me wish I had carbs. I love the starting and idle quality and the MPG. But, new carbs set up properly can come real close to EFI performance overall and even exceed top end.

Good luck.

Re: MPI to Carb ??
 

Carb = simplicity, EFI = potential nightmare. Often problems with a carb motor can be diagnosed quickly and easily, with EFI the potential problem list becomes endless. When they run fine EFI is great but when they dont it is a pain. Carbs are much easier to deal with.

Re: MPI to Carb ??
 

duke nailed it - more HP/$$ with a carb...especially if you include troubleshooting time and money.

Re: MPI to Carb ??
 

EFI in my car is great. But I'm not trying to modify my car. I've read way too many stories of people building EFI, and having to send the computer back 3 and 4 ++ times trying to get it right.

Auto Zone has Holley parts. They don't have a computer programmer. :D

Re: MPI to Carb ??
 

Saw your post about going to carbs. I'm actually looking to go to MPI from a carb. I'm not looking for the extra HP and want the reliable start and fuel economy. I'd be interested in buying you EFI set up if you're planning on selling. Would you need my intake?

Just thought I'd throw out the food for thought.

Re: MPI to Carb ??
 

nash give me a call or give me your number mine is 203 913-5450

Re: MPI to Carb ??
 

In a car due to the partial loading on the engine at various rpms, EFI has a huge effect on fuel economy.

In a boat, that load vs rpm range is much, much narrower. So how much really with EFI save vs a well set up carb? Not much I would guess.

Re: MPI to Carb ??
 

I agree. Probably saves gas at low RPM but going faster, you need a certain amount of gas to produce HP, so MPI, EFI or carb, my opinion is it's gonna need the same amount of fuel... I'm old school but I'd choose carb... plus I'm able to work on it by myself...

Re: MPI to Carb ??
 

I switched to carbs this past year because I was tired of trying to get additional hp without any luck from my mpi's. I had a carb motor for 10 years prior to these engines. So, I knew some of the downfalls but were outnumbered by the positives.

Re: MPI to Carb ??
 

When I bought my boat the dealer talked me out of MPI and I'm glad he did. My carb,set up by Mr. Nickerson, it's perfect first time out 2 pumps hit the key and it's running. Rest of the day I just bump the key and it's running. The key to this equation is the carb set up and Mr. Nickerson has that key covered.

Re: MPI to Carb ??
 

I also have a carb on my 7.4L, 454. I grew up working with carbs, so they seem simple to me... rebuilding, adjusting, etc... EFI seems high-tech, but god only knows to to fix it.

The rebuild kit for my carb I did this summer was $150 dollars. Expensive, but I rebuilt/water-tested/tuned in a day. Now the boat starts perfect (three pumps when cold), idles perfect and flys at WOT. Best of all, no labor fees.

Tom

Re: MPI to Carb ??
 

I forgot to mention emissions is probably the single biggest reason EFI went into boats...and cars! Without EPA regs the automotive industry would have taken much, much longer to make the change.

As for me, I kinda don't care what comes out my boat's exhaust! :evilb:

Re: MPI to Carb ??
 

My boat is carbed, but it's equiped with a new fangled device to help start it when it's cold. It's called a choke.

Once I've started the engines first thing in the morning, they fire up before one full revolution of the engine the rest of the day.

Re: MPI to Carb ??
 

It could be quite a bit actually. Ever looked at the air/fuel ratios by cylinder on a carbureted engine? They're terrible, and they get worse with load. You have to richen the carburetor, so the leanest cylinder doesn't get too lean, and then the rest of them are wasting fuel.

One of the problems with the marine EFI is there is no air meter as you have on today's automobile engines, so any engine changes automatically result in the need for computer recalibration. They also don't have the level of onboard diagnostics cars do.

If automotive EFI is any indication, someday I think everyone will be using it in boats. Compared to carburetors, my automobile EFI has been infinitely more reliable and better running. I've never had to do a thing to any of my car EFI systems, but I've sure had a lot gasoline on my hands rebuilding and troubleshooting carburetors (yuch!).

Michael

Re: MPI to Carb ??
 

I don't have a choke and mine do the same thing :p :D :D

Re: MPI to Carb ??
 

There are so many advantages to fuel injection and computer controllled engines that I can't list them all. Suffice it say that this is a wave that will not be stopped. The older Merc fuel injection is kinda primitive but is still better than a carb in stock apps. A good tuner like Tyler Crockett can also make a lot of horsepower with them. The new PCM555 is another jump in technology but still lags behind the auto market. In the next few years the marine builders will have to catch up because emissions regs will force them. Although there is a learning curve involved and some things will be beyond the scope of a backyard mechanic the up side is that the systems get much more reliable as time goes on. Also in my experience many of the so-called problems with fuel injection are not FI related at all. Bad gas, ignition system problems, and internal mechanical failures are still the most prevalent failures on FI engines. It's just that the FI system is like some mysterious boogieman that you can't see into so it always gets blamed. Reminds me of the days when every tech blamed the ignition module if the car wasn't running right. The downside is that techs have to become computer savvy and invest in tools like the Rinda program to rule out computer issues in the first place.

Re: MPI to Carb ??
 

The problem may not be fuel related, but I can look down a carb and see if it's getting fuel.

Re: MPI to Carb ??
 

No one can debate that EFI and the computer can make a lot of things happen that couldn't happen without it. The new ZO-6 at 505 hp and 20++mpg would no way be possible without it.

But on a boat, if you want to make performance upgrades, the computer has to be changed. Sure, we can buy the scan tool or the laptop software to see where something is wrong, but those won't change it. You have to have the tools and the knowledge to do that. Tyler can and does make great HP with efi engines, but he is able to do the reprograms that 99% of us don't know how to do. Thats where the problems come in with efi. change your heads/cam/ignition, and then the whole system needs to be reprogrammed. If Tyler is building my engine, that easy, he sets it up and its done. BUT if I am building my engine its a whole other story. Thats where a carb works. Most of us know how to set them up, and get the engine to take advantage of the changes.

Re: MPI to Carb ??
 

If you get serious about converting, I am in the market for an EFI wiring harness and maybe an intake.

Thanks,

Kirk

Re: MPI to Carb ??
 

I'm in the same boat. I am building 2 383's from my old MX 6.2's The cost of reprogramming them is upwards of 1000.00. I am seriously considering going carb, making the changes so everything works onthe dash, and selling 2 efi systems. I guess there is some tuning software available isn't there?????

Re: MPI to Carb ??
 

I've been thinking about getting a 29 Scarab w/ twin 350's. I assumed I could pull and sell the complete Merc engines (EFI included) and replace w/ a couple of kickin' 383 carb motors for very little cost differential. Maybe I'm just dreamin...but I think +400hp carb'd 383's can be had cheap.

Re: MPI to Carb ??
 

I will have about 10K in both of mine, reusing one block, and buying a new replacement block for the other. :evilb: