Modern 350 Marinizing

Discussion in 'DIY Marinizing' started by LMannyR, Jul 8, 2007.

  1. gonzo
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    gonzo Senior Member

    Tanks in boats are not exposed to air like in a car. There is no radiant heat escaping. Also, engine compartments are closed and get very hot after stopping the engine. Fuel will boil and cause hard hot starts. A fuel cooling system prevents that. A return line into the tank makes it pressurized which raises the question of how to make it comply with regualtions. It is possible but more expensive and complicated than using a already made for marine applications system. I believe that only as a hobby it can be justified because of the extra time and expenses .
     
  2. broke_not
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    broke_not Junior Member

    I understand what happens during a "hot soak", but it almost seems as if you're trying to say that fuel injection systems are somehow inferior in such situations. The industrial stuff I'm comparing boat applications to, also has enclosed engine compartments, enclosed fuel tanks, etc. There's absolutely no comparison between a carbureted and fuel injected engine when it comes to which setup is superior....EFI wins every time. Higher pressure in the fuel lines, and constantly pumping the fuel in a loop has made fuel percolation a non-issue.

    Add to that the fact that when not running or cranking the injector(s) are switched off, (whereas a carburetor bowl sitting there full of gas and exposed to the high underhood temps during a hot soak can dribble into the intake as the fuel heats up and expands making hot-starts difficult), and I don't see how EFI can possibly be thought to be a disadvantage....
     
  3. gonzo
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    gonzo Senior Member

    I think you are misunderstanding, I am talking about marine EFI
     
  4. broke_not
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    broke_not Junior Member

    How is marine EFI any different than any other EFI? What on a marine fuel injection system makes its performance characteristics/reliability/advantages any different than any other non-marine EFI system?

    This in particular is what I'm wondering about:

    Every EFI setup I'm aware of is less prone to heat issues than a carburetor setup would be in the same application.....regardless of what that application may be.

    Whether by accident or design, the very things that cause issues such as you described have been dealt with, (and done away with), in an EFI system.
     
  5. gonzo
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    gonzo Senior Member

    Yes they have. That is why a marine fuel injection system works better on a boat than an automotive type. Also, it is legal. I am not sure what are you disputing. Where did carburetors come into the discussion. Perhaps you need to go back and read the posts before arguing a point or claiming I am making one.
     
  6. broke_not
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    broke_not Junior Member

    Well, starting from page one:

    Not all automotive EFIs use a tank-mounted pump. In-line ones are easy to obtain and can be mounted pretty much anywhere.

    Then there's this:

    What would cause "fuel overheating" in an EFI setup?

    Once again, how are EFI systems affected by the heat? The fuel being pumped in a loop, coupled with the higher pressures in the fuel lines make EFI systems pretty bulletproof when it comes to dealing with heat.

    They didn't....directly. But after you mentioned the supposed issues EFI systems have dealing with heat, enclosed areas, etc., it certainly sounds as if you're implying that one of the characteristics associated with EFI systems is that dealing with the hot environments isn't their strong suit. Then again, perhaps you were just commenting in general about marine fuel systems having to deal with heat....and not EFI in particular. But if that were the case, why list the supposed heat issues right after the statement about the problem of having to run a return line?

    :?:

    Just for fun, I had two other people read the posts in this thread.....and they came to the same conclusions I did.;)

    :D
     
  7. Art_H
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    Art_H Junior Member

    A few points;

    1. Not all EFI auto systems use a fuel return system.
    2. The high pressure fuel pumped into fuel rail meets a pressure regulator, where the excess fuel is bled back to the the tank. This return line should not be under high pressure as there is no resistance back to the tank.
    3. How is a 'heat soak' in a marine application any worse than the hottest season in southern US for auto EFI in engine bay?
    4. The truth is that 99% of carbs on any vehicle have not been tuned correctly. It is possible, certainly with the wideband O2 sensors now to make a carb almost as efficient as EFI, but it still cannot account for all the changes in power demand.
    5. The cost and pain of refitting the EFI was mentioned. I personally would give a lot of effort to gain more fuel efficiency.
    6. Why would an auto EFI system not be marine aproved? Provided marine distributor etc. The 'MARINE' EFI uses all auto parts anyway I'm sure.

    Biggest reason to go EFI, California is making some emmissions changes in a big way... a preview of the future. Like it or not, EFI may even be required on all boats in the future.
     
  8. TollyWally
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    TollyWally Senior Member

    Art,
    It is my understanding that the marine efi systems don't use o2 sensors in the same fashion as automotive systems. Others more knowledgable may correct me.
     
  9. Art_H
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    Art_H Junior Member

    No, not all do. I think the newer ones are. It is mentioned in the exhaust manifold sales info about having a bung for O2 sensors. That may just be for tuning purposes then pluged.

    There are plenty of examples of EFI systems that do not run O2 sensors.

    With the old style O2 sensors, they were not accurate anywhere except Stiochiometric @ 14.7:1 A/F. So it would move the A/F ratio back and forth over this ratio. At wide open throttle, the O2 is ignored anyway. O2 sensors not required, though much better with, certainly way better with the wide band O2. It just takes a little tuning. That alone is advanced for most people though. Like I said, most carbs are not tuned even in the ball park to where they could be. Carb tech is quite complex to understand fully, and even have the adjustments on the carb.
     
  10. gonzo
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    gonzo Senior Member

    Art_H
    -Which automotive EFI don´t use return line?
    -Return lines are not under high pressure, but under pressure anyway. It causes some legal and safety issues that are avoided by the marine version.
    -The heat soak is worse because a boat engineroom is closed
    -That 99% of carburetors are not properly adjusted is not true. If you are going to quote numbers in a forum of engineering geeks, please do your homework and don´t insult us with baloney
    -How is a O2 sensor of any kind going to make a carburetor more efficient?
    -Approvals are made by government or other organizations for specific applications. If it is approved for automotive use that is the scope of the authorization. It has nothing to do with whether it may work in other applications.
     
  11. TollyWally
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    TollyWally Senior Member

    Hey Art,
    I've got a new set of freshwater cooled manifolds for my BBC. It is my plan when I swap manifolds to install a steel plate spacer between the risers and the manifolds and tap it for 02 bungs. I think it will keep them dry enough to work, but it is a bit of a guess. My main motor dude thinks it will work and the new manifolds require some fab work anyhow so I am going to give it a shot. I was aiming for spring but now I will put it off till late fall. I'm not going to run efi but I do want to be able to tweak my carb and get some numbers to tune with.

    I have a holley 650 spreadbore with vacuum secondaries. It is a model 4100 and DOES NOT have the detachable float bowls. I had to do a little remachining on the carb due to some stripped needle valves. Long story. I am still dialing it in and am having a few difficulties. I am not real experienced with carbs but hey I'm the guy that has to do it. Right now I think I have the secondary float set wrong. It's dribbling fuel into the secondaries at low rpm and flooding it out, I think.

    In any event do you or anyone else out there have much experience dialing in a carb. I can use all the help I can find, LOL :). I have a fuel flow meter that I use religiosly and I figure later with an o2 reading I can get her dialed in as tight as possible for my cruise speed. I have a quick change kit on the diaphram for the vacuum secondaries and can play with that. Right now I can cruise where I want just before the secondaries open.
     
  12. gonzo
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    gonzo Senior Member

    What number power valve do you have?
     
  13. TollyWally
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    TollyWally Senior Member

    I think they are 6.5's
     
  14. gonzo
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    gonzo Senior Member

    That is in the middle and should work. Make sure the gasket on them is the correct one. They are two types. If you use the wrong one, they will leak like you describe.
     

  15. TollyWally
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    TollyWally Senior Member

    Gonzo,
    Do you mean the wrong gasket on the power valve will cause the carb to dribble fuel into the secondaries at low rpm?

    I have been assuming my float level was set incorrectly or my float was sticking. I did take a powervalve off and look at it to see what size it was. I put it back together with the old gasket which looked fine. I am fully capable of creating problems for myself. LOL
     
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