carby or fuel injection

Discussion in 'Sterndrives' started by ajbale, May 20, 2007.

  1. ajbale
    Joined: Dec 2006
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    Location: mackay queensland australia

    ajbale Junior Member

    I am in the process of rebuilding my 454 bbc, was after an opinion on fuel consumptoin, a well tuned carby or fuel injection, i have to purchase a manifold, inectors etc to do this. Is this cost worth the it? The engine is pushing a 25 foot boat of around 3 tonnes, and uses about 55 litres an hour a 45 to 50 kph, in gallons i think its around 14 to 15 per hour, and about 25 knots, anyone who owns a fuel injected or mpi engine is welcome to reply on what they use, and what its pushing.
    cheers.
     
  2. StianM
    Joined: May 2006
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    Location: Norway

    StianM Senior Member

    A fuel injection system will allways give you a litle extra milage/hp, but you are also likely to pay more for a fuel injection system then you are for a carb.

    I think eatch person have to find out this by themself.
     
  3. Steve in SoCal
    Joined: May 2007
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    Location: Woodland Hills, California

    Steve in SoCal Junior Member

    You are not going to see much savings from port injection and no saving from throttle body unless you are running a very rich mixture with a carb. Injection is much better on cold starts and is cleaner under light loads. A well adjusted carb will deliver good power and fuel mixture at a contant speed. The injection is good when changing altitude where mixture changes with air pressure but on a boat that is not much of factor. The other thing is that carbs seem to work better with low engine temps, an injection system is warm up mode at 180 degrees unless you can reprogram it.

    While carbs are old school and have some quirks they work well and on a boat where the engine is up on throttle all the time, mixture is very good with a well tuned carb. A better bet would be a cam designed for your use and power range.

    Steve
     
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  4. redtech
    Joined: Feb 2007
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    Location: suger pine, ca

    redtech Senior Member

    just inject it: better fuel economy, less maintenance, quick start up, more power, less worries and don,t have to worry about the fuel in the system going bad while storing (in the system does not include the tank)
     
  5. u4ea32
    Joined: Nov 2005
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    Location: Los Angeles

    u4ea32 Senior Member

    A carb you can fix. EFI you can't. And your mechanic won't be able to either. You will never measure a fuel savings, but you will easily measure a big chunk of cash disappearing to pay for the EFI, and then the unbounded efforts to try and fix it when it does not work.

    With a conventional carb, its very easy to diagnose. Too much / too little fuel? Carb. Lousy spark? ignition. Hard to kill.

    With EFI: every signal goes to the computer, which then adjusts everything. As your sensors and (worse) connectors degrade (corrode), the signals your EFI computer will read will get less and less accurate. The responses will become more and more inappropriate. What causes it to be too rich? Anything! To have not enough air flow? Anything! Detonation? Anything! Stalling? Anything!

    EFI in a car: yes of course.
    EFI in a boat: If you keep it on the road, no problem.
     
  6. ajbale
    Joined: Dec 2006
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    Location: mackay queensland australia

    ajbale Junior Member

    thanks for the advice
    arnold:)
     
  7. redtech
    Joined: Feb 2007
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    Location: suger pine, ca

    redtech Senior Member

    one more thing on EFI vrs. CARB, over here in the states volvo penta, mercruiser , and marine power all sell fuel injection over carb.
    and for my two cents fuel injection is eazier to fix than a carb and not as badly misunderstood. then agian i do this for a living
     
  8. ajbale
    Joined: Dec 2006
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    Location: mackay queensland australia

    ajbale Junior Member

    Just a question about the price of a fuel injection system over there in the states including manifold, fuel rails, injectiors, fuel pump, throttle body etc, from start to finish?:?: :?: :?:
     
  9. redtech
    Joined: Feb 2007
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    Location: suger pine, ca

    redtech Senior Member

    edelbrock mpi kits start around 2150.00 to 2500.00
    holley mpi kits 2300.00 to 3800.00
    holley tbi kits 2700.00
    most likely labor to install around 8-12hrs if engine is out and boat is present
     
  10. extremejet
    Joined: Jun 2007
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    Location: qld

    extremejet New Member

    here's my 2 cents worth..
    been running a 350 with carb with minimal problems (the odd bit of crap stuck in the needle & seats, worn accelerator pump diaphragm, nothing too major) cheap and easy to fix and tune.
    now running a merc454 with mpi...(MEFI1 ecm)
    was running sweet with no problems but once something goes you need to be einstein to fix.
    even my mechanic with his scan tool is scratching his head.
    basically was running really rough (missing) between 2000 and 3000rpm.
    if you could get over that seemed to run ok.
    put scan tool on and found between that rev range spark advances to about 40.
    have replaced dist. with new one (ic module inside dist.)
    had codes 33 (map sensor) and 42 (ign.control)
    by removing and re-inserting connector to map sensor was able to clear 33 but not 42...ran fine for a while..then not.
    once again removed map sensor connector and ran fine again (although still slight miss (popping noise) at about 1500rpm
    Still no idea whats going on ..have sent ecm to technician to see if he can sort it out.. hoping they may be able to reprogram it or something.
    Otherwise it's time to buy a new manifold and carby..unless someone has any better ideas???
     
  11. u4ea32
    Joined: Nov 2005
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    Location: Los Angeles

    u4ea32 Senior Member

    Very similar to what was happening in my EFI engines. Finally replaced the entire engine wiring harness. Mercruiser just needed te serial numbers, and they sent two new harnesses. Gradually remove the old, plug in the new.

    Takes a couple of days, not hours.

    Found lots of differences between the two engine harnesses -- some connectors looked perfect on one engine, and corroded on the other, some individual pins were bad while others were fine.

    Since, the engines again run as well as ever. But the cost was many, many thousands to NOT isolate any cause, and then $6K to replace the harnesses.

    Would have been a LOT cheaper to go to carbs, and I would if I had to do it again.

    No possible way that any fuel burn difference between EFI and carbs can ever make up for that amount of time and money spent fixing this problem.
     
  12. StianM
    Joined: May 2006
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    Location: Norway

    StianM Senior Member

  13. krush
    Joined: Jun 2007
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    Location: VA

    krush Junior Member

    for what it's worth. Previous owner of my boat (26 foot nova II spyder, T454) put an aftermarket fuel injection system on it (made by hirel/cutler, eventually bought out by holley). It's a nice system with nice equipemtn but the damn ECU was old fashioned and you coudln't tune it. It ran ok, but not as good as my friends identical boat with stock carbs.

    FIRST...an aftermarket EFI system HAS TO BE TUNED otherwise you will get worse performance than a carb. If you don't know what I talking about, stick with carb.

    Back to my boat. Guess what I'm doing right now! I found stock carbs, intakes, mechanical fuel pump, and carbs used off another boat. I'm putting them back on. The boat had been running like ****, but the straw was that I was getting water in the oil because the damn manifolds were aluminum and corroded away in the coolant crossover. They may still work on a car after being cleaned up, but the tiny bit of oxidation made a bad seal and I got water in the oil.

    Let's just say I expect her to run much better once I'm done. If you were getting a new motor from mercruiser/volvo, I'd say go EFI, but not doing an aftermarket deal. You will never see the return on investment.
     
  14. Frosty

    Frosty Previous Member

    EFI is great on cars. If it goes wrong you get out of the car and go home.

    A boat is not like this, it could leave you stranded in dangerous situation.

    A carb can aways be repaired or tinkered with but most importantly rarely gives up to such an extent that the engine wont run.

    A 4 barrel spreed bore with mechanical secondaries on a dual plane inlet manifold will give good torque and idle speed control.
     

  15. Steve in SoCal
    Joined: May 2007
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    Location: Woodland Hills, California

    Steve in SoCal Junior Member

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