Safer carburettor in a box?

Discussion in 'Inboards' started by tom kane, May 22, 2014.

  1. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Even the simplest single point EFI performs better in terms of efficiency and reliability than any multi jet carb, that alone makes carbs a thing of the past except for very small engines.
    And for the manufacturers the benefit is that EFI is cheap. From the submerged pump to the injectors everything is molded plastic except the injector nozzles, upgrading means just writing new data in a memory chip.

    They could make the connectors a bit better though, but that would increase their price. The contacts themselves are pretty well protected with a silicone seal, but the back has just a flimsy sleeve that allows water to reach the crimped terminals.
     
  2. Ike
    Joined: Apr 2006
    Posts: 2,496
    Likes: 353, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    Actually there was one. It was made by PCM specifically for Mastercraft, but I can't get into details as because I believe it is still considered proprietary (trade secrets) We at the USCG HQ spent a lot of time looking at this system and requiring changes to it that would lessen any risk of fuel being sprayed into the boat. But that was 13 -14 years ago and I do not believe they still use that technology.

    Yeah that was me, and others. I can't take all the credit. LOL. The whole point of requiring the fuel pump to be within 12 inches of the engine, or mounted on the engine is to minimize the length of pressurized fuel lines. You do not want pressurized lines running through the boat. One pin hole leak or leaky fitting and the entire contents of the fuel tank go into the bilge. This is also the reason for no pressurized return lines. They can use a gravity feed return line.

    EFI has many advantages, it virtually eliminates vapor lock. With computer sensors for O2 and fuel it regulates fuel into the engine far better than a carb, resulting in more power, better fuel economy, smoother running, instant starts and and no power lag when accelerating. But you can't use a pump in the tank and you have to have a means to turn on the electric fuel pump for a few seconds prior to start, to pressurize the line from the pump to the injectors. This is because of the requirement that the fuel pump not be running when the engine is not running. But it wouldn't work, because the EFI system has to be pressurized for the engine to start. So the pump has to run just long enough to get the EFI up to start the engine. There are a few other specific requirements for EFI that are unique to boats.
     
  3. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    How does that differ from automotive EFI?
    The pump runs until enough pressure is sensed or for a fixed time, than it stops and only resumes when the engine is started. It is a safety requirement for both gasoline and diesel engines. Some manufacturers even add a deceleration sensor to cut off power on impact.
     
  4. Ike
    Joined: Apr 2006
    Posts: 2,496
    Likes: 353, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    It's not any different, but was prohibited by the Federal Regulations. Now it is allowed. It's consider part of the starting of the engine.

    Sec. 183.524 Fuel pumps.
    (b) Each electrically operated fuel pump must not operate except when the engine is operating or when the engine is started.
     
  5. tom kane
    Joined: Nov 2003
    Posts: 1,767
    Likes: 48, Points: 58, Legacy Rep: 389
    Location: Hamilton.New Zealand.

    tom kane Senior Member

    I am not disputing the beauty EFI Technology but showing safer carburetor thinking when it was not available. There is probably still more carburetor equipped boats in use at present than EFI. Have a poll.

    The photo of the Opel motor fuel system was taken because it was used as a test-bed and it did do what it was intended for and contained and removed fuel from the carburetor flowing down over the exhaust etc.,. many carburetors can leak fuel from the fuel_in line fitting. The fuel needle valve can leak and stick.
    The fuel level can be set too high. The fuel level can tilt when the boat starts to plane.
    Adjusting the fuel level can be complicated using different thickness of washers and other means and requires a running motor check to get it right and may show a leaking carb. Carburetors often warp and do not fit properly body-to-float chamber and the gasket becomes in-effective.This is near impossible to repair properly. There is a big list of possible "flooding carburetor " causes.
    The trend is to have back-up technology and even light aircraft can have a "spare set of wings" in the form of a parachute and these have saved lives and property.
    It is possible to "go over the top on safety"?
     
  6. Ike
    Joined: Apr 2006
    Posts: 2,496
    Likes: 353, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    Which Opel engine is that? Which Carb? I was the proud owner of three Opels in the 70's and early 80's. That carb looks a lot like the 2 barrel solex that was on the two Mantas I had. The engine was a 1.9 liter overhead cam. In 1975 Opel changed it to a mechanical Bosch fuel injection.
     
  7. tom kane
    Joined: Nov 2003
    Posts: 1,767
    Likes: 48, Points: 58, Legacy Rep: 389
    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Right on all counts Ike. Holden Sunbird served us well. Had two spare motors 200k miles no bother. The overhead chain drive cam was dirty though it sprayed oil vapor everywhere and most finished up outside the motor it used a lot of oil. Cam belts would have been a great improvement. But I still liked it.
     
  8. powerabout
    Joined: Nov 2007
    Posts: 2,916
    Likes: 63, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    Tom
    marine carbs cannot spill fuel, hence why they are modified from their automotive versions.
     
  9. tom kane
    Joined: Nov 2003
    Posts: 1,767
    Likes: 48, Points: 58, Legacy Rep: 389
    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Marine carbs can spill fuel much the same as an automotive carb can by way of the means I pointed out in my previous post #20. If I had a marine carb in my family boat I would want a back-up but I would use a remote fuel system anyway.
     
  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 482, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If the needle valve sticks on a marine carb, the bowl floods and over flows into the venturi, through the bowl vent J tube or body drilled passage. It doesn't over flow the bowl and spill on the engine.

    Most carburetor engines, have their carb base plates shimmed to a typical trim state and is a standard practice when designing a propulsion system. In fact, repower, applications often have to use different base plates for this reason. Flooding or spilling doesn't occur at the usual angles of trim seen in a boat, no more than a car climbing or descending a steep hill. If you have a craft that has an unusually high trim angle range, you can install a gimbal mounted float in the bowl and it does exactly the same thing, as those employed on off road racers, prevents bind and over angling the float. I've never seen a marine carburetor that needed a gimbal mounted float, but they're available.

    If you have a warped carburetor body, then you can file it, though it's usually best to just toss it in favor of a reliable one. This isn't particularly common, unless serious neglect and age is involved, neither of which can be accounted for from an engineering stand point. The same is true of leaking fittings, which are easy to find, repair and prevent.

    Modern EFI systems use a fuel pressure regulator with an internal check valve, which maintains pressure from the engine mounted regulator to the injectors. Automotive systems are similar, though have different "hoops" to jump through, in regard to EPA and fuel consumption standards. This is why you see the pressurized systems in cars, to save every last drop and seal the system (relatively) from vapor leaks.

    Yes, you can have too much safety engineered into a product. The ballistic chutes you mention are an option and only on quite small craft and interestingly enough not especially popular, holding a very small percentage of the market. It seems you're looking for things to over engineer (maybe some British blood there? :)). EFI has been in the industry for a long time and a huge percentage of sales are EFI, not carbureted. Leaks and flooding are the result and responsibility of the owner, which is another issue that can't be engineered out of the equation. When you look at the investigative results of boat fires, several reoccurring themes keep cropping up. The boats were older and in poor repair, which resulted in a situation, often a combination of issues. I investigate these types of events regularly and it's very rare to be surprised. A boat sinks and after inspection a 30 year old thru hull is to blame, imagine that. A boat burns and a non-marine approved fuel pump was employed from the local auto parts store, imagine that. A leaking fitting that had a single non-marine clamp, a just plain too old part was asked to perform once too often, etc., etc., etc. The results are rarely surprising. What do you think the percentage of new, first time boat owners, backing their fresh and shinny pride and joy in at the ramp, sink or swamp, because they didn't know about the transom plug? Well, maybe automatic transom plugs, because we have to protect and secure the truly brain dead among us too.
     
  11. Ike
    Joined: Apr 2006
    Posts: 2,496
    Likes: 353, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    Par is right. I too have investigated a lot of boat accidents, in particular fires and most are due to lack of maintenance or just plain "cheapness". Replacing marine parts with auto parts or cheap materials. Accidents on shiny new boats are almost always "pilot error". Yes, defects do happen on new boats, but more often than not they are discovered and corrected before they cause a problem.

    Right on Tom. On my 71 Manta at about 60K miles a single bolt for the chain guide came loose and threw the chain out of alignment, causing the whole thing to lock up. I had to tear the whole engine down to replace the chain and sprockets and ended up doing valves, rings, bearings, all seals, etc. But those were damn fine cars. I wish I still had them. I later bought a 73 Manta which was my commute car in San Francisco when I wasn't van pooling. They were a blast to drive. I also had a 67 Kadett that went over 200K. It's problem was a really fragile manual transmission. Had to rebuild it twice.
     
  12. tom kane
    Joined: Nov 2003
    Posts: 1,767
    Likes: 48, Points: 58, Legacy Rep: 389
    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Thank you Par for your frank and informative discussion and I agree with most of your opinions.
    Many people will never be able to keep up with the expense of up-grading all of their possessions and boats will be low on the list. It would be nice if we could be able to spend as we please but we have to make choices and some times it may appear be the wrong choice to others because and we can not afford to comply with regulations or even the Law, we have to be tolerant of that. We can not stop doing things we like to do.
    Discussing carburetor equipped boats has to take into account the time and available equipment at that time and the country and economic situations I think past History of boats and designs is very interesting and attempts to improve things by others.

    I would be interested to know what you think of long-tail boat engineering.

    As for safety experience has taught me to make my own decisions after much research and thought and I do not know how to play follow the leader and that has often saved my life.
     
  13. powerabout
    Joined: Nov 2007
    Posts: 2,916
    Likes: 63, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    I've never seen a petrol engine fire that was caused a component failure and if it was it was so old it had rusted away and generally not on the engine.
    The USCG did a good job with those rules and that was a long time ago they made them.
     
  14. Ike
    Joined: Apr 2006
    Posts: 2,496
    Likes: 353, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    Thanks, but in the spirit of full disclosure, they were lifted almost word for word from existing industry standards in the 70's. Most of them were already in ABYC, BIA (the old Boating Industry Association, now NMMA) NFPA, UL, and SAE standards. We, (the USCG), just changed some of the wording to please the lawyers and published them as a proposed rule making.

    So in reality, the boating industry already knew what needed to be done. The Coast Guard just made it law.
     

  15. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 482, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Agreed Peter, most manufactures had already addressed most issues, before the mandates came down from the USCG. The concerns of carburetor leaks and fires as a result, aren't justified in the statistics and though possible, certainly not practical nor price point justifiable.

    EFI as a bolt on replacement for a carburetor is about 10 times as much as just a new carburetor. Given this, most just opt for the new carb, with many trying to rebuild, often unsuccessfully. I've rebuilt dozens of carbs and they can only take so much, before the body is warped, the shaft holes are "egged out" etc. and the thing just has to be tossed. Knowing when this is required does take some experience, but I do think the average person rebuilding a 50 - 60 year old baby, realizes that they're working with spent parts and looks at replacement or a better example of the old part he has. Swap meets and specialty suppliers abound in this regard, particularly with old outboards.

    These bolt on EFI replacements don't have to be the spider nest of wires, typical of the earlier generations. The new units have just a few wires, the fuel management computer is self contained in the throttle body and it's as easy as bolting it to the intake and starting it up, so it can "learn" what your system needs. I've installed a few of these systems and they're fool and bullet proof. Of course you're married to a throttle body style of injection unit, but these are fine for up to 400 HP. I've seen systems rated for more, but in most cases, if you need more, you'll be considering sequential injection and other "power adders".

    I'm currently active in a high HP (700+) racer that I designed a few years ago. They're debating the benefits of switching to required EFI. The usual current setup is a tunnel ram and twin 4's, but these are less desirable than the advantages of fine tuning a single or duel throttle body, with it's related, fuel, timing and temperature adjustments available. They really don't produce more power, but they are much more tunable for conditions and can make these adjustments on the fly, underway. Try that on a carb setup at 90 MPH. The only thing holding back the rules committee is the adjustability of the typical packages. Picture a dyno tested 700 HP engine that with some prompting from a dash mounted interface, suddenly cranks 750 - 780 HP during the race. Not good for the fairness of the class to say the least. They may eventually permit EFI, with interface lock outs, etc., we'll see. NASCAR faced the same issue a couple of years ago and now do permit EFI, with certain ajustability features locked down.

    I guess it's just the same level of evolution we've come to hate. Gravity feed or literally drip feed was replaced with low pressure systems, now these are replaced with high pressure systems and us old farts are having difficulty "growing" with the change. I can just see the old fart bitching about the newfangled spark plug, when he insists on the burning ember method as being just fine or the man complaining about the unman like need to push a starter button, instead of hand cranking. A bunch of weenies we are . . .
     
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.