Please note this thread has been inactive for 90 days. For the best results, please start a new thread.
Results 1 to 25 of 25
  1. #1
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default 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. #2
    Ensign Ned L's Avatar
    Join Date
    Sep 2008
    Location
    CT
    Posts
    963

    Default 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. #3
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default 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. #4
    Commander scipper77's Avatar
    Join Date
    Sep 2008
    Location
    Rochester, NY
    Posts
    2,043

    Default 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. #5
    Seaman archcityBob's Avatar
    Join Date
    Nov 2010
    Location
    Saint Louis, MO
    Posts
    52

    Default 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.

    ~Bob

  6. #6
    Petty Officer 1st Class capslock118's Avatar
    Join Date
    Apr 2009
    Location
    New Haven, CT
    Posts
    247

    Default 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.
    Engine:
    Make: Mercury 2-Stroke Outboard
    Model: 135hp V6 BlackMax
    Year: 1990
    Serial #: 0C261104

    Boat:
    19' Open Bow SeaRay 180

  7. #7
    Petty Officer 1st Class Water logged's Avatar
    Join Date
    Nov 2008
    Location
    Arizona high country
    Posts
    256

    Default 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.

    Glenn


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

  8. #8
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default 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)
    119,216
    Regular Unleaded Gasoline
    114,100
    Regular Unleaded Gasoline/10% Ethanol (E10)
    112,000
    Regular Unleaded Gasoline/15% Ethanol (E15)
    110,129
    Compressed Natural Gas (CNG) 87,600
    Liquefied Petroleum Gas (LPG) 83,500
    Ethanol (E-85) 81,800
    Ethanol (E-100) 76,100

  9. #9
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default 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. #10
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default 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. #11
    Supreme Mariner roscoe's Avatar
    Join Date
    Oct 2002
    Location
    Medford WI
    Posts
    18,127

    Default 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.




  12. #12
    Lieutenant Commander
    Join Date
    Aug 2001
    Location
    Pensacola FL USA
    Posts
    1,514

    Default Re: Converting to CNG?


  13. #13
    Petty Officer 1st Class raymondpickens's Avatar
    Join Date
    Aug 2010
    Location
    Pleasanton, TX
    Posts
    260

    Default 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. #14
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default 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. #15
    Ensign
    Join Date
    Jun 2010
    Location
    South Metro, MN
    Posts
    996

    Default 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.

  16. #16
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default Re: Converting to CNG?

    Necessity is the mother of invention! If people are forced to either give up their fishing/skiing trips or find a solution, I bet someone comes up with a solution right quick.

    I hadn't thought about 2 strokers though. There are some "diesel" trucks now running on CNG. It has become economically viable given the distances traveled versus fuel savings.

  17. #17
    Moderator Bob_VT's Avatar
    Join Date
    May 2001
    Location
    West Rutland, Vermont, United States
    Posts
    24,364

    Default Re: Converting to CNG?

    PM QC and ask his advice...... he works in the industry and is a pro about CNG............
    This is a great link to boat specifications http://boatspecs.iboats.com/
    Please, shop iboats first!!


  18. #18
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default Re: Converting to CNG?

    Perhaps he will find this tread and comment

  19. #19
    Vice Admiral NYBo's Avatar
    Join Date
    Oct 2008
    Location
    Orange County, NY
    Posts
    5,539

    Default Re: Converting to CNG?

    Quote Originally Posted by ttugrad View Post
    Perhaps he will find this tread and comment
    Yeah, no PMs. We all want to know!
    Bob
    '88 Bayliner 1700 Capri Bowrider, 85 HP Force O/B, "Sea Weasel"
    Want a vessel safety check? Click here. Want to join the Coast Guard Auxiliary? Click here.
    Disclaimer: Although I am a member of the USCG Auxiliary, the opinions and advice in my replies are my own and do not necessarily reflect CG or CG Auxiliary policy or regulations unless so specified.

  20. #20
    Rear Admiral Fireman431's Avatar
    Join Date
    Sep 2007
    Location
    DeBary, Fl
    Posts
    4,247

    Default Re: Converting to CNG?

    This has been discussed at length here before. Anyone search for it first?
    2001 Carver Voyager 374 'Stick's Competition'

    Something tells me I should be on the water....

    If I answer your upholstery questions, it's only because I've been doing it 20+ years...

  21. #21
    Seaman ttugrad's Avatar
    Join Date
    Sep 2010
    Location
    Lubbock, Texas
    Posts
    70

    Default Re: Converting to CNG?

    I did do a search and some items came up about cars and trucks, but nothing specifically about boats.

    Care to share the link?

  22. #22
    Moderator QC's Avatar
    Join Date
    Mar 2005
    Location
    Chino Hills, CA
    Posts
    22,026

    Default Re: Converting to CNG?

    There are some misconceptions in this thread, but there is also some pretty good info. Some key points to clarify:

    As others have mentioned, methane (primary constituent of natural gas) is lighter than air at ambient temperature and pressure. For vehicle storage there are two methods, compressed (CNG) and liquefied (LNG). CNG is typically stored at either 3000 or 3600 PSI, and this is the critical safety issue. LNG is methane that is super cooled to -259 F and stored in cryogenic vessels (dewars). Both are used extensively on-highway, and yes . . . drum roll . . . some in Marine.

    The most popular use in Marine is probably with mega LNG tankers. They use the boil off gas (another long discussion regarding LNG) to supplement their large diesel engines in a combustion process called dual-fuel. This combustion process, used for on-highway trucks, is what I do for a living. Another long discussion that has been covered here I think in Dockside and Non-Boating Technical. The LNG tankers (ships) use it because it is kind of free. The fuel boils off during transport anyway, so they inject it into the engine and light it off with diesel or preferably bunker fuel (big ships):



    There are also LNG ferries operating in Norway where this is becoming fairly popular. There is a CNG Ferry in British Columbia, but I am not sure it is still in operation.

    So somehow, some way, there has been marine certification for both although these were compression ignition (diesel) engines in all cases (no spark plugs).

    I also know of some LPG boats in the UK. I've actually seen them for rent and assume there are more applications there, but I have actually seen these. So again, somebody insured, and hence "approved" them. But I have never seen CNG in a pleasure boat and there are quite a few reasons why. Let's assume you could get an engine "kit" for a 5.7 (you can), and a bigger assumption is that you could make it legal. Here's why it might not be that great:

    1) Fuel density

    The gallon equivalency info in post #8 is a little confusing. Here for reference is the questionable piece:

    Quote Originally Posted by ttugrad View Post
    Fuel Type BTU Per US Gal/Equiv.

    Regular Unleaded Gasoline
    114,100
    . . .

    Compressed Natural Gas (CNG) 87,600
    The problem is they are showing a "gallon" of CNG and they've got it wrong. Since CNG is a compressed gas, how can they define a "gallon"? The other fuels shown are liquid and can be compared by that volume unit, but can't really do that with CNG. LNG yes, at -259 F, LPG yes at -44 F which are their respective boiling points, and how they might be able to be counted as a "gallon". If you look at the comparison of those fuels though there is a very useful piece of info, BTUs per gallon. And, for simplicity, CNG is usually sold in Gasoline Gallon Equivalents (GGE). So you have to figure out how to store (and buy) 114,100 BTUs of natural gas to get the same energy as a gallon of gasoline. If you look at your gas bill, you probably pay in Standard Cubic Feet (SCF). An SCF is around 1000 BTUs, so you need 114 SCF to get that GGE. That's basically a 5 ft cube at ambient pressure. Not really practical for anything. But when squeezed to 3600 PSI we can get a GGE into the same space as around 4 gallons of gasoline. In other words you need 4 times the space for the same amount of fuel. This is why you usually only see CNG on light duty vehicles.

    2) Weight

    Since it's lighter than air, the more you store, the lighter your boat, right? Well, of course not. When you "weigh" the CNG in a GGE it is actually about the same as a gallon of Gasoline. What, say 7 pounds? That's not the issue. Four times the tankage, and those tanks must be able to safely handle 3600 psi and they're suddenly VERY heavy. Say 500 lbs for 25 gallons . . .

    3) Cost

    Carbon Fiber tanks are expensive and you have to buy the fuel system and you have it installed if you could. Let's use $5000, but it would probably be twice that.

    4) Payback . . . (the killer of almost all pleasurecraft fuel saving ideas)

    Let's say we save 1.00 on a GGE, could be as good as $2.00, but use $1.00 and if you want to cut the payback period in half, that's OK, but pretty aggressive. So let's say you use 25 gallons a weekend, and you boat 20 weekends a year = 500 gallons. This is a lot, but it's a simple example. If we save that buck, it would take us 10 years to get even, and that does not take into account the time value of money. If you use less fuel per year, then payback period is longer. Baaaaaad investment, put the $5K in the bank and buy gasoline. Done.

    P.S. We can talk LNG if you want, but basically you need your own station and that would require a use of around 10,000 LNG gallons per week to be very practical. This is why I chase trucks. A fleet of 20 can do that in some cases.
    Last edited by QC; April 8th, 2011 at 03:01 PM. Reason: Fixed lost pic??? Replaced with quote box.

  23. #23
    Ensign Ned L's Avatar
    Join Date
    Sep 2008
    Location
    CT
    Posts
    963

    Default Re: Converting to CNG?

    Thanks for correcting me on natural gas being lighter than air. I should have looked it up before commenting. That does open it up to being an interesting concept.

  24. #24

    Default Re: Converting to CNG?

    Quote Originally Posted by ttugrad View Post
    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.
    This would actually require a tank 50% larger.

  25. #25
    Admiral smokeonthewater's Avatar
    Join Date
    Dec 2009
    Location
    indiana just n. of louisville
    Posts
    6,994

    Default Re: Converting to CNG?

    welcome to iboats and kudos for searching but this is an old thread and nobody is asking anymore
    Kevin

    Quote Originally Posted by Tinnie
    But, where are the reevets?
    1981 Wellcraft V-20 CC Fisherman (FREE BOAT)
    1989 Wellcraft Monte Carlo 28(Build thread here)
    1992 Hotsports Jet'n'Cat Yam 701 WR3 drivetrain "SS George Washington"
    90's Yamaha WRIII and a pair of 95 Kawasaki ZXI-900's
    Fresh clean cheap oil is better then old dirty expensive oil any day

Similar Threads

  1. Converting a mec 200 EFI to 225
    By ar in forum Mercury & Mariner Outboards
    Replies: 1
    Last Post: November 8th, 2010, 09:10 AM
  2. Converting
    By kb3gup in forum Johnson & Evinrude Outboards
    Replies: 6
    Last Post: October 30th, 2010, 11:06 AM
  3. Converting a 200 to a 225-250
    By cnallick in forum Johnson & Evinrude Outboards
    Replies: 5
    Last Post: June 6th, 2008, 09:39 PM
  4. Converting to EFI
    By crazysammy in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 3
    Last Post: August 10th, 2007, 03:40 AM
  5. converting
    By rfdking in forum Mercury & Mariner Outboards
    Replies: 11
    Last Post: March 19th, 2002, 03:36 PM
  1. iboats Forum Directory - Over 100,000 forum posts organized by topic