Looking for some guidance
I'm currently swapping a 454 /330 with a carbureted 502 mag and both engines are out of the boat.
Would the addition of the efi kit in the]below be a good way to improve power and driveability?
One caveat is I plan on running stock manifolds and thru hull exhaust, would adding this conversion be a waste with stock exhaust and or would I risk reversion?
[ATTACH=CONFIG]518320[/ATTACH

THANKS

i saw that setup for sale, you have the right motor to do it on also. i really don't know how you can go wrong switching to EFI, it is the future, hell its become the present. if i were you and i bought that setup i would throw exhaust on it. you should be able to get some gils or similar for under 1000 bucks.

What kind of ECM are you gonna go with? EFI isn't created equal these days is why I ask and your future plans play into what system is best. I chose Holley HP MPFI, however, my expected power is around 625hp, so the flexibility and tune ability of this kit is much better than most. Have you asked Alex Haxby about this? Very knowledgable guy.

It's not that you will gain a ton of HP. That's not why most guys go EFI, however being able to actually pull fuel and timing is something you can't do with a carb on the fly. It kinda is what it is... Start ability, fuel distribution, and on the fly adjustment are some of the big reasons to switch. There is also efficiency to be had, however the gains become smaller when running WOT all the time. I'm no expert, but have been reading up, and have had tons of help from Alex, as I purchased my kit from him. Might not be in your budget, but seriously consider ditching those merc exhaust manifolds.

that kit he is looking at has a Arizona speed and marine ecm that Is programed to work with a 502 and the cam that is included with it. I am not sure if he has future mods in mind but that should be a bolt on and go setup if I am not mistaken.

If I didn't own the EFI stuff already, or have a great deal on it, I'm not sure it's "worth it" to change. Unlike a car that sees a thousand different throttle input changes an hour and needs to precisely meter those changes, a good setup carb in a boat will deliver the same or comparable efficiency as an EFI at set throttle positions, plus allow adaptability and modifications for performance changes at a substantially lower cost and expertise. JMHO, I could be wrong!

That couldn't be further from the truth. With the advent of self learning EFI, you don't have to be a tuning expert. A carb is incapable of adding fuel in the curve. They are crude at fuel delivery. And not all EFI is comparable. You should read "EFI for everyone", as you will soon realize just how inefficient carbs truly are. And you are leaving out one very crucial thing, timing control coupled with superb fuel delivery. You definitely have every right to your "opinion" but those do not trump these "FACTS".

There also is the option of buying a used 525 take off and having Dustin doing a tune for your specific combo.
This work's real well, and all the safe guards of smartcraft.

You missed the "Worth" part. All you say is true to some extent. Air fuel/ratio is an air/fuel. timing curve is a timing curve. EFI isn't magic, it's just a more efficient way to achieve those goals by "mapping" smaller intervals of time. If all you ever dealt with is EFI then that surely is the easiest. I don't need to read a book, I've stood likely hundreds of hours over a real dyno with real motors of all configurations, so I have some basis for my opinion in real life. All can be achieved with a good carb set up and proper distributor curving. In in a boat for god's sake, who cares about efficiency! LOL! On the dyno, a good tune carb motor will make as much horsepower as an EFI. A/F ratio, curve, when it's right, motor don't care where it came from.

Now-- back to the question as I understand it, is the perceived difference in "efficiency" WORTH IT to purchase every piece of hardware and software necessary to make a Carb motor an EFI motor. My opinion is no. You won't notice a seat of the pants difference for the $5-7000 per side it would take. Buy EFI motors, start with EFI motors, build EFI motors, I just don't think converting a perfectly good carb motor to EFI nets gains worth the expense.

I love EFI, everything I've built in the last 7 years has been EFI, I'm a true believer, so you're preaching to choir. I just don't want this guy to spend $10k and get 0-1 MPH gain and be upset. That's the reality, whether it's your reality or not.

Who ever said he would spend even near 10k? And being that you are experienced, you should know that there is a definite difference in fuel distribution when comparing MPFI to carbs. Carburetors also will never hold a candle to cold start ability of EFI. Nobody, including myself had made the claim that "EFI", as generic as that term is, can somehow automatically increase horsepower in every application! However a MPFI system can add and subtract fuel at certain RPM. Can your carburetor do that?! Didn't think so. As you know, EFI compensates, carbs do not. Yes they can work very well in a marine application, albeit crudely.

That said, do I think everyone needs EFI? No. And my reason isn't because of Hp, efficiency or start ability even. It's COST/BUDGET for a scenario such as this one. With the new self learning EFI, it's about cost of admission, not which is "better". Cost being the only consideration, obviously the carburetor wins.

The reason I went to MPFI (Holley HP to be specific) were many. Start ability, improved idle, better fuel distribution, and flexibility with my build. I'm not here to convince this guy of why EFI is better. The facts have been tabulated, carburetors are dinosaurs. But in some situations, within certain platforms and budget constraints with said platforms (ie stock engine with stock manifolds and no real plans for much in Performace) carburetors can work well enough. The death of the carburetor is immanent, much akin to the death of the PC. It's happening in all forms of mororsport ( NASCAR) . It's just going to take some time.

Better stated than I did Borgie, I guess the point was if you have a working, good carb set up, then the advantages you mentioned are have to be weighed by cost. To build an engine, I would never consider a carb in the build plan unless money was a constraint. I was simply making the point that the performance, particularly in a boat, doesn't necessarily justify ditching one working system over another. If he was having problems and needed to buy new carbs, hell no! But you know you just don't 'swap' EFI onto a motor. Fuel delivery, spark control, wiring, exhaust mods for Oxygen sensors, and a host of unseen goblins, all have to be calculated in addition to the swap, plus the cost of labor if he isn't mechanical. True? You pay a boat shop $90 an hour, $10k is chump change for two engines.

I clearly see the day when carb production will be outlawed. Emission standards on boats are coming! But here's some real facts: My Scarab has twin 460 Chevys (.30 over) and with some dyno time, put out 508hp at 5800 rpm. That's 1.10 hp per ci. Mercrusier 525 EFI puts out 525 hp with 504 Cubic inches, or 1.04 hp per ci. Starts are never an issue on my boat. One pump cold, fires. Warm, can't get my hand off the key fast enough. bulletproof. My buddy with twin 525s in a fountain goes the fuel dock as much as I do. I can't justify EFI to gain so little. But that's just me.

I was only trying to give ol' Stimleck another viewpoint. To build an engine, I would never consider a carb in the build plan unless money was a constraint. However in the issue of conversion, he might be better served from a performance standpoint to spend some money on cam, intake, heads, exhaust and get the girl breathing better and enjoy it and save the EFI for the next boat. I didn't intend to get into a carb vs. efi discussion. There really isn't a discussion. Let me repeat, I LOVE EFI. But, I truly believe if 90% of the boaters out there didn't know what they had under the motor cover, they'd never know the difference. Carry on!