[C38] New Owner w/ CNG question

Tue Dec 22 09:16:21 EST 2009

Hello gentlemen,

I can't imagine a problem converting from CNG to propane.  I've done several natural gas to propane conversions on home heating units and with them, the only thing you do is reduce the jet size to make a more oxidizing (lean) flame, otherwise you will have a reducing (rich) flame if you don't reduce the jet size.  I do heating and air work on the side and have done several home conversions from natural gas to propane and vise versa on heaters and hot water heaters. 

I have never bought jets for a natural gas to propane conversion.  I use a small hand held collet chuck drill bit holder with a set of small drill bits. I start by finding a drill bit that fits the old jet exactly and make a note of it. I then solder up the old jet and drill through the solder with a smaller drill bit.

If there is any yellow in the flame, I repeat the above procedure going to a smaller drill bit and check the color of the flame again.  I repeat the above procedure until the flame is totally blue with no yellow showing.  A blue flame indicates complete combustion with absolutely minimal O2.

Some stoves, hot water heaters, and HVAC central home units offer their products with conversion jets to make the conversion from propane to natural gas or visa versa but sometimes there are small other differences between the two product lines other than just the jet.  Whatever the differences are, they must be minimal because from comparing two seemingly identical space heaters for different gasses, I could not see any differences other than the jet sizes but the manufacturer listed totally different part numbers for the two units so there must be some small difference.

As simple as a boat range is, I doubt there would be any problem changing the jet size and trying it.  If the procedure wasn't satisfactory, just drill out the solder and return the range back to stock.

I would be highly surprised if changing the jets to a smaller size wouldn't produce a perfect conversion but since the conversion is so simple and cheap, why not try it if your range and oven is in good shape otherwise?

Not only is propane cheaper and easier to find than CNG, it also provides more BTU's for more efficient tank efficiency.

One property of CNG that was highly praised in the 70's when it first became popular for boats was that CNG is lighter than air and would not concentrate in bilges making shipboard use safer.  In actual practice, some boats have been blown up with CNG from overhead cabin lights making little or no difference in actual safety experiences between the two gasses in enclosed vessels like ours reducing the popularity of CNG.

Anyway, that's my two cents.  As I type this, I'm sitting here keeping warm near a non-vented gas space heater converted from propane to natural gas.  Propane to natural gas is an easier conversion than visa versa because all I needed to do was enlarge the jet instead of making it smaller making soldering the jet orifice unnecessary.

Tom Troncalli
Renata #95

----- Original Message ----- 
From: David Epstein 
To: Catalina 38 Listserve
Sent: 12/22/2009 1:23:11 AM 
Subject: Re: [C38] New Owner w/ CNG question

Hi Jay,

Congratulations on your "new" boat, and welcome to the C38 family.    I know Broad Reach very well.  We used to race against them, and I even raced on it a couple of times. 

I have never had any problems finding CNG.  You can get it a gas dock that is not too far from San Diego Yacht Club (SDYC) in Shelter Island in the SD harbor.   I think it might be called Pearsons Marine Fuels. You don't have to get your tank filled, you just remove yours, exchange it for a full one, and you  are on your way.   In fact, I always try to get a tank when we are in SD as they seem to put a bit more gas in the tanks than they do in Marina del Rey.   As I recall, you get as much as 2300 lbs, and we are lucky to get 1900-2000 lbs in MdR.

Personally I would not consider changing to Propane, unless you are planning to spend a lot of time in Mexico or other areas outside So Cal.   CNG is lighter than air, making it much safer than Propane, which will settle in the bottom of the boat.   

Let me know if I can be of any help to you, and again, welcome.

David Epstein
C38 #122, SuperStar
Marina del Rey, CA

At 01:17 PM 12/21/2009, you wrote:

Greetings All.  We recently purchased C-38 Hull # 311 “Broad Reach” with the original CNG system.  The boat is going to be a San Diego boat and I was wonder what other So Cal owners have done to fill their tank.  Is there an exchange site around, do you use an adaptor and fill at the auto stations, or has everyone given up and converted to propane?  Love the boat overall, but this CNG issue may be a hassle for weekend cruising.  Would also like to hear from other C-38 owners in the area to exchange ideas and information.  We can be contacted off list at jsorensen at novarx.com

Thanks!

Jay & Dorothy Sorensen
C-38 #311 “Broad Reach”
San Diego, CA
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