Converting from CNG to Propane

Apr 10, 2017
91
Seidelman 37 Kemah, TX
Considering a '86 40' Legend. Looks good except for CNG stove. Has anyone experience with converting that to propane?
Thanks,
Bob
 

KD3PC

.
Sep 25, 2008
1,069
boatless rainbow Callao, VA
it is usually changing out the regulators and the orifices on the stove and other appliances. Adding a sniffer or two for propane. Given the age of the gear - you may just want to replace things and get another 30 years of service.
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
A propane locker vented overboard, and a solenoid valve are required for propane. The gas line should be enclosed in tubing running back to the locker. There's a lot to it, I recommend getting a professional to do it.
 
Apr 10, 2017
91
Seidelman 37 Kemah, TX
Just curious as to whether there is room or a good place for the propane locker.
 

Rick D

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Jun 14, 2008
7,023
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Unless you are going to Mexico or the islands for an extended time, you might consider getting a second CNG tank and an adapter for a fueling station fill up. Huston has a ton of them and there may be many near you also.
 
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Apr 10, 2017
91
Seidelman 37 Kemah, TX
Where is your CNG cylinder now?
Don't know, haven't looked at the boat yet. Thought maybe someone had one and could tell me if the CNG tank location would be suitable for a propane locker.
 
Feb 26, 2004
22,020
Catalina 34 224 Maple Bay, BC, Canada
if the CNG tank location would be suitable for a propane locker.
Generally, no. CNG tanks are long and heavy, like oxygen tanks, and can be installed down below because CNG is lighter than air. Propane tank boxes need to be installed higher up, usually in cockpit lockers, because the boxes need to have a hose from the bottom that leads outboard. Look in the West Marine Advisors for details.
 
May 24, 2004
6,843
CC 30 South Florida
Propane stoves have thermocouple valves that will shut off gas in the event that a burner flames out. CNG stoves are not equipped with such valves as the lighter gas would dissipate in the air where propane will pool like water in a low spot. Many have done the conversion but it just requires constant supervision while the stove is in use.
 
Apr 10, 2017
91
Seidelman 37 Kemah, TX
Thanks for all the responses. Sounds doable, but maybe more trouble than it's worth.
bob
 
Feb 2, 2006
453
Hunter Legend 35 Kingston
I did a conversion to LPG on my 87 Legend 35. There is a space under my aft starboard helm seat that is sealed from the inside, and drains overboard, and fits a 5lb-8lb LPG tank (tight fit, but manageable). I added solenoids, and sniffers. It was a fairly long route to get the hose to the stove, but I ran it under the structural grid on the port side so it's out of harms way.

I managed to get a new set of orifices for the original stove and it works reasonably well. As noted above, it does not have thermocouples and thus requires some extra care, but I have two sniffer sensors installed to help mitigate the safety issue. My stove it a "mini" version with 2 burners, and a "broiler" instead of a proper oven (really just burns the top of things), so installing something new would require some re-configuring of the galley area and sacrificing storage the is currently below the stove.

My options were limited. One by one, the places to get a CNG tank filled disappeared, until the closest was 3 hours away. I started the process of getting a second tank, but eventually gave up and just converted.

Chris
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
... One by one, the places to get a CNG tank filled disappeared, until the closest was 3 hours away. I started the process of getting a second tank, but eventually gave up and just converted.
+1 to Chris. You might want to check for local CNG refill stations before you spend money.
 
Feb 14, 2014
5,790
Hunter 430 Waveland, MS
That's a joke, right?
Not at all.
They are Propane Professionals. The convert, make hoses, do safety checks, install tanks, and sell propane.
I use them all the time for my home, boat and other propane needs.
Jim...
 
Feb 14, 2014
5,790
Hunter 430 Waveland, MS
I just looked up on the web A Propane Specialist near Kemah.
They SELL Propane.
How you sell more propane? See my post#15

That's a joke, right?
Are you joking?:solame:
Jim...

PS: I have propane service in my home. They check 2 times a year for leaks[free], Made me a propane hose to run my Grill with a quick connect coupling[free], fill my 500 gallon propane tank[$$], to run my whole house propane emergency generator.:dancing:
As a home design/builder, I use a Propane Provider to install all piping, tanks, valves, etc [Free for my clients], but clients must buy propane for 5 years from the propane company.
 

jviss

.
Feb 5, 2004
4,627
Tartan 3800 Westport, MA
The guy asks about converting a CNG setup to propane on a boat, and you give him a link to a residential propane delivery company. Have you ever heard of people getting propane delivered to sailboats?

And what's with all them "lame" emojis? How old are you?
 

TomY

Alden Forum Moderator
Jun 22, 2004
2,671
Alden 38' Challenger yawl Rockport Harbor
Thanks for all the responses. Sounds doable, but maybe more trouble than it's worth.
bob
I was going to do just this, with my boat, 15+ years ago. When we had kids onboard coastal sailing in season, we went through quite a bit of CNG. I can remember going through 1 tank a week during a two week cruise.

What that means: The smaller CNG bottle is called a 20 hour tank: A 4,000 btu typical stove burner would burn for 20 hours.

Back then, the local CNG exchange would give me a new bottle and take the old, for about $60 bucks. CNG, btu per btu is ridiculously expensive compared to propane.

The conversion would have been easy compared to creating a propane locker. That is a project on our boat.

We've never had a problem finding CNG exchanges in New England. Plus we keep two tanks onboard(in a nice arrangement where the tanks slide back into an aft unused area of a cockpit locker), so you have plenty of time to get a back up.

Today, I think there are more options for CNG exchanges in our area.

These days, with mostly just two of us - and we cook quite a bit onboard for coastal sailors - a tank lasts us almost all season. We exchange one bottle a year, easily, a few miles away. Price has gone up, exchange is about $70. It's definitely not worth converting for us.

Find out if CNG is hard to get where you plan to cruise, and figure out how much gas you use cooking, then look at what you have to do to convert?
 
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