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CliffB

EFI for older carb'd Malibu

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CliffB

I'm wondering if anyone has installed electronic fuel injection on an older Malibu originally equipped with a carb. For fuel efficiency and smooth running I would think this would be a nice upgrade.

I see there's very basic systems using a single large throttle body and a single injector, but that doesn't look too efficient to me. I'm really thinking of separate port injection with a good fully electronic high-pressure system.

Are there any systems out there like that for less than say $5K? Does anyone have any experience setting one up and getting it to run how it should?

Thanks.

Edited by CliffB

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Lance B. Johnson

Man what a fun project cliff! I would do the work for free I love this kind of stuff.

I think it will be difficult to find an aftermarket marine system though? What about rounding up the parts from a total?

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Michigan boarder

I'm playing devil's advocate here. How much do you expect to gain in economy and smoother running? Have you done a rebuild on your current carb? I think it might be a lot of money for negligible gains.

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Devin Perry

When I had my 87 SS I looked into doing it and found only a few companies that had marine setups. One of them is here http://www.affordable-fuel-injection.com/ixxocart/products/Chevrolet_Marine_MPFI_System-25-41.html

It would def. be a fun project. I decided not to do it on mine. I didn’t feel it really added real dollar for dollar resale value to the boat and I was already planning to go to a newer boat in the future

.

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Devin Perry

I agree with Michagan boarder also I was not content with how the boat was running so I started looking into options. When I decided not to go injected I took the Q-jet to a profesional rebuilder and after they were done the boat ran great and was a pleasure to drive. I think the gains would be minimal but there is the FUN project factor that you need to consider.

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Falko

Want to increase your performance? Get an Edelbrock performer gap aluminum intake, and an Edelbrock marine carb. I replaced the FI system on my '99 Mercruiser with this set up, better performance overall. Quicker holeshot, quicker throttle response, and increased top speed. That gap intake runs a little cooler as it is separated from the engine.

I still have my old FI setup (I think) if you want to play with it. But it is cast iron (HEEEAAVVYYY) and I don't have a controller for it ($$). I personally wouldn't waste my time with it.

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Woodski

As Falko indicates, a well tuned carb setup will actually outperform an FI setup (specifically from a power comparison), but is a bit more finicky and prone to need some adjusting over time and might not get quite the fuel economy of a good FI system but really not much difference. If you chase after his FI setup, a MEFI 4 controller is what you would need to complete the system.

The carb on a Mercruiser is a Weber 4bbl which is the same as a Carter or Edelbrock, but with a 3 step needle rather than a 2 step needle. It is rated at 750 cfm so more than adequate for a 350 CID engine @ 5,000 rpm. As for the the airgap intake, a boat has a 140 degree stat, so you are not going to see the same gains as a car would see since there will cooler water running through the manifold and no real airflow in the doghouse compared to a car's engine bay. The water also helps the warm up portion if that is a concern. If you are out shopping for one anyway, it would be the better choice and the aluminum will save weight.

If you are after increased performance, there are numerous more cost effective items to put on the list: heads / cam / exhaust / 1.6 ratio roller rockers and if you don't want to spend much/any money: ignition timing / carb blueprint & tuning (there are several items to improve response and performance on the Weber/Carter/Edelbrock carb). David Vizard authors a great book on the subject. If your boat has a Holley, lots of experts and information on those to fine tune them.

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Nitrousbird

This is a good thread on a TBI conversion. I've been very very tempted to do the same.

This right here says it all. Even a properly tuned, rebuilt carb doesn't perform as smoothly, start as easily, and run as consistently as EFI. Hell, NASCAR has even given up on Carbs. :) I will never own another boat with a carb.

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CliffB

Thank you fellas, interesting comments and thoughts all, for sure.

I would agree that the performance gain with a well set up EFI will be modest, if not minimal, over a well tuned carb. But, EFI will run very smooth and reliably if done right, and should show a meaningful fuel savings. I would guess (WAG) that EFI would improve fuel consumption by a good 15-20%, particularly if it was a good direct port injection system (8 injectors). So, if I was burning 5-6 gallons an hour at cruising speed (~25-28mph) with a carb then I'd be closer to 4-5 gph with EFI. That would be nice, especially considering I only have a 25 gallon tank in my old Skier (Mercruiser 5.7 MIE260 with Rochester quadrajet).

Frankly, what I'd like to do is put Weber 48IDAs on my Skier but the dog house won't clear them. Not even close, so there goes that idea. The quadrajet I have works fine (I rebuilt it) and runs quite smooth, I just have to believe that a good EFI set up will add a bit more hp/tq and a bunch more efficiency.

Thanks again, I'll do a bit more digging and see what I can come up with.

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Woodski

Cliff - Some data for your analysis, there are 5 boats we have used to ski behind (4 Bu's, 1 MC), ranging from carbed Echelons to Responses. Fuel consumption differences across all the Bu's are not measurable so I doubt you will see a 15-20% difference going to EFI. Our ski laps are very consistent and repeatable. I totally agree that EFI will be simpler, provide better cold starts and might have better mixture control. It is worthwhile to note that engine vacuum and distance from carb to intake valve provides a good area for atomization.

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Falko

I bow to Woodski on his engine knowledge and the comments on the intake, and would definitely agree that 15-20% increase in efficiency will not be seen unless you are dumping raw fuel through your engine to the water currently.

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tradershipp

We had a 1989 Malibu Sunsetter, Euro F3, Rochester Quadrajet. It ran perfect for 20 years. Yes, it took a few turns to start cold, but after I learned to pour a little gas down the carb it started like a fuel injected engine. We started having inconsistent idle problems so I rebuilt the carb, the local shop rebuilt it, still had idle problems. Thought I found the problem when I found tons and tons of carbon on the back sides of the intake valves. This engine had 950 hours on it. So I rebuilt the top end, new exhaust manifolds and all new hoses. Still would not idle consistently. I double checked for vacuum leaks and did not find any. I decided to add TBI fuel injection and bought a kit from "Affordable Fuel Injection" - $1620. What a mistake. The only improvement was cold start. Everything else was a nightmare. It never idled correctly and would die when placed in gear sometimes, could not be relied upon. This is really tough when pulling up to a dock or trailering it. This engine never died with the carb, never. It also had a very bad flat spot at around 2800 - 3500 RPM, flat out would not run between 2800 and 3500 RPM. It was a nightmare trying to hold skiing speeds. AFI reprogrammed the chip several times with no improvements. We used it for about 2 months, saw no improvement in efficiency, if you ran it at higher speeds, it seemed to use more fuel than the carb did. No difference in power/speed. I returned the unit within the return policy, AFI "repaired it" and sent it back to me. They kept saying I installed it wrong. They would not return any money. They do not stand behind their warranty and will not accept a return, so don't even think about doing business with them. I reinstalled the Quadrajet and it ran just like before. We traded it in on a new 2013 VTX, I was honest with the dealer about the problems it had.

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martinarcher

Still got that kit?

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tradershipp

No, do not have the kit anymore. I sold it on Craigslist for $550. Nice looking Sunsetters. Ours was similar. We really loved it and had a bunch of fun. It will be missed.

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Edited by tradershipp

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