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Converting to CNG?

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  • Converting to CNG?

    With gas prices being what they are and all of the talk about new proven natural gas reserves in the US, what about converting your boat engine to run on natural gas? I run a sterndrivre and automotive conversion kits are available. I Googled it and found no information on the subject. Is this possible and if so, what are the possible pitfalls/advantages?

    Thanks in advance.

  • #2
    Re: Converting to CNG?

    I suspect you won't find any conversion kits that are U.S.C.G. approved, and without that you 1) would have a hard time selling in the future, and 2) would have a real uphill battle with insurance if anythign went wrong. Besides, isn't nautural gas heavier than air (?), so every little leak will collect in the bilge & cause an explosion concern (more so than gasoline because this source is under pressure).


    • #3
      Re: Converting to CNG?

      Just bouncing ideas off here, but wouldn't a common blower that all I/Os come with alleviate the problem of settling natural gas?


      • #4
        Re: Converting to CNG?

        I hope I'm not wrong on this butt....

        I had a recent gas leak at my house and the tech that came out to fix it told me that natural gas is lighter than air. If that was the case then that alone is a good reason to run natural gas in boats.
        Most people are going to do whatever they want. What I find entertaining is how people justify what they do!!


        • #5
          Re: Converting to CNG?

          A fast google .... CNG (compress natural gas) and Natural gas are lighter than air. Propane, butane and Liquefied Propane gas are heavier than air.

          A copy/paste from e how dot com ...
          Compare CNG vehicles with LPG for suitability and performance. Given the bulkiness of CNG vehicle tanks, these vehicles are less spacious. LPG/CNG vehicles are known to have a slightly lower initial pickup but greater acceleration. You may experience cold start problems with these vehicles. It is also important to check for the availability of LNG/CNG in your area to know if you can have consistent fuel supply. LPG fits best with light vehicles such as cars and small vans that run on petroleum, while CNG is ideal for heavy vehicles operating on diesel.

          1972 Deck Boat, 16 feet
          2006 Dodge Dakota SLT 4 x 4 Quad Cab


          • #6
            Re: Converting to CNG?

            Besides, isn't nautural gas heavier than air (?),
            Natural gas is lighter than air; it's propane that's heavier.

            I'd be curious to know how safe, or lack of, a tank filled with a compressed gas of any kind would fare in such rough conditions as being on water in a boat. Be it flat water hauling at full speed or 5' waves whatever; it's not like a car which, unless you are in an accident or going off-roading, is a much smoother ride.

            I know I wouldn't want to move my air compressor when it's full of air.
            Make: Mercury 2-Stroke Outboard
            Model: 135hp V6 BlackMax
            Year: 1990
            Serial #: 0C261104

            19' Open Bow SeaRay 180


            • #7
              Re: Converting to CNG?

              For me a major concern would be refueling. I drop my boat in and it stays in the water for 5 to 14 days. I can buy gas on the river or carry it in gas cans. Neither would be an option with CNG. With propane it would be possible to use 5 or 10 gal. tanks. I don't see any CNG pumps being installed on the river any time soon.


              08 Sun Tracker Regency, Party Barge 22
              08 Mercury 115 hp 4 stroke


              • #8
                Re: Converting to CNG?

                Found this on ETC Green.com:

                Fuel Type BTU Per US Gal/Equiv.

                Diesel (Ultra-low Sulfur) 129,800
                Bio-Diesel (B-20) (sourced from plant oil) 128,500
                Bio-Diesel (B-100) (sourced from plant oil)
                Regular Unleaded Gasoline
                Regular Unleaded Gasoline/10% Ethanol (E10)
                Regular Unleaded Gasoline/15% Ethanol (E15)
                Compressed Natural Gas (CNG) 87,600
                Liquefied Petroleum Gas (LPG) 83,500
                Ethanol (E-85) 81,800
                Ethanol (E-100) 76,100


                • #9
                  Re: Converting to CNG?

                  Using this chart, CNG has roughly 77% of the energy per gallon equiv. of the E10 gas that is used now, for my purposes I'll call it 2/3 the energy. If CNG was used and took up the same space as gasoline, and I am not sure if it does, you would need to have a 1/3 larger "tank" to get the same distance as a tank of gasoline.

                  I get what you are saying about refueling, but you could carry smaller tanks of CNG to and from your boat as you would gas cans, hook them up in-line and be on your way.


                  • #10
                    Re: Converting to CNG?

                    yeah, but you do carry your BBQ tank to and from the place that you get it filled, don't you?


                    • #11
                      Re: Converting to CNG?

                      The size, weight, and cost of the system are all major obstacles. As is the 24% drop in btu/gallon, and the lack of refueling facilities.
                      Medford, WI


                      • #12
                        Re: Converting to CNG?

                        Read this:


                        • #13
                          Re: Converting to CNG?

                          Ever tried to use propane to unclog a pipe or something where you introduce the gas to water, Its the best mosquito attractant around.
                          Old enough to know better, still too young to care.


                          • #14
                            Re: Converting to CNG?

                            Interesting article that makes sense. Currently it is probably not to your financial advantage to run CNG. I would wager that the cuurrent issues causing oil prices to skyrocket are only going to get worse, forcing us to use more of the fuels that we have "on hand" in the US. Major reserves of NG have been located and are able to be utilized with a relatively new process called hydrocracking. That along with the presence of an existing delivery infrastructure say to me that we all will be running our cars, trucks and boats off of CNG in the not too distant future.

                            Conversion will be needed for existing engines and since people tend to keep boats and motors forever it might be a good thing to start considering.


                            • #15
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                              Re: Converting to CNG?

                              Might be a matter of impracticality. Eliminate 2 strokes and diesels from the dance card. Unlikely such a kit would be deveolped for 4 stroke O/B's anytime soon, leaving only the gasoline marine 4 strokes automobile based engines. Develop a kit, get it certified for marine use, and you have what would very likely be a very expensive conversion.
                              For some reason anything with the "Marine" label on it costs multiple what the same thing for the car/truck world does!
                              Then there is the refueling issue. At least around here, there are few refueling stations, and nothing even close to convenient. Dragging the boat around on a trailer burning tow vehicle fuel would get really old, not to mention waste tow vehicle fuel.
                              Not sure how practical it would be to drag a grill tank sized container around- what would the range be?
                              Natural gas cars and trucks would have to be out for quite some time before anyone would likely develop anything for boats. I personally don't see it as a viable option at this time. But you're right in that we have a very large quantity of NG available right here in the good old USA.