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I don’t have a sense of how many here use CNG on their boats. The fact that it is lighter than air is appealing from a safety standpoint. Apparently the supplier to many marinas in the Northeast / New England (Corp Bro’s?) was acquired by a large foreign company that has suspended or discontinued deliveries to marinas for exchange. My yard in Rockland ME said to start thinking about converting to propane.

In searching for another source of tanks I came across this CNG fleet supplier who will refill “in compliance” tanks at their Tewksbury MA location. They just need to have a days notice since their locations are self service but to fill the typical marine tanks they would need to have technician there.

AVSG
Mike Manning 617 571-8122
20 Maine St
Tewksbury MA 01876

Just thought I’d pass this along to anyone in the same boat. (Pun intended)
 

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If I had CNG I would look to converting to propane. it would disqualify a boat purchase.

Lots of hoops in Annapolis area to find re- charge compared to propane. No doubt you need a good monitoring system checked at least yearly to insure safety.
 
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So I can sail to Salem or Marblehead and rent a car for the 25 mile drive to Tewksbury (avoiding rush hour or it will take a LONG time) if I call ahead and can arrange for someone to be there to refill my tank. Assuming that they think a typically screwy sailboat tank passes muster for refilling at a location 25 miles from any harbor. Though it may be safer than propane, CNG does not sound like a super-viable option at this point. That the information in the original post might actually help someone with a CNG stove shows how difficult refilling CNG tanks has become. Maybe electric induction would be better.
 

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Discussion Starter #5
Since I already have CNG and frequently travel between Philly and Maine this location is not a hassle for me. It’s right along my route. I would not go with CNG if currently comparing with propane but don’t want to convert unless I have to. Finding and building a vented location for a propane tank would be more of a hassle than getting a tank filled once a year. CNG vehicle filing stations might be an option in other areas.
 

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Since I already have CNG and frequently travel between Philly and Maine this location is not a hassle for me. It’s right along my route. I would not go with CNG if currently comparing with propane but don’t want to convert unless I have to. Finding and building a vented location for a propane tank would be more of a hassle than getting a tank filled once a year. CNG vehicle filing stations might be an option in other areas.
Once a yeAR. You must not use your stove/ burners very often.
we also use the same propane tank for our grill which we use very frequently
 

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Yep, it's over for CNG in NE.

We'll limp through this season with one CNG tank and a propane burner that we found which fits nicely on the stovetop. That plus a propane Magma grill which is quite versatile we're finding. We steamed two lobsters on it last week nearly as fast as a stovetop burner (not to mention all the water vapor kept outside).

I've been eyeing the benefits for next season:

A 5-pound propane tank which takes up an 8" X 12" space, holds 107,955 BTUs.

Regular (not the longer-larger volume tanks) CNG tanks yield a "20-hour burn"; which they rate using a 4,000 BTU burner running for 20 hours(perfect world - in reality, I bet all fills vary of any gas).

An apples to apples comparison shows the LPG 5pounder will yield nearly a 27-hour burn.

Two LPG 5 pounders should yield 54-hour burns which means nearly equivalent to 3 CNG tanks. These days, with two onboard for more than a month, we'll use 2 CNG tanks for the season.

10 pounds of LPG will be more than ample. Why go to a bigger tank?

Further, the volume for the two LPG tanks, if you have to build a locker, will need a vented locker about 10" X 17" X 13". Compared to my two side by side CNG tanks in a rack that is about 12" X 20" X 24".

The little tanks will be easier to haul weighing about 10+ pounds full compared to CNG tanks weighing,... 40 pounds?

And of course, the savings for me in the above would be enormous as we're paying about $90.00 USD per CNG exchange here in mid-coast Maine.

So there's a look at the bright side of going from no-kaboom to BIG KABOOM!!! 😂

Just kidding. We use propane onboard and at home and are familiar with the slight added risk onboard.

My problem so far is locating the conversion parts for our CNG burners. I have this winter to sort that out. The rest is straight forward for us.

Working with a friend who will have to locate a vented locker below decks. That's the tricky part. I suspect there will be quite a few conversions next season unless something changes.

We're lucky to already have a space above decks with plenty of room for two, even three 5 lb LPG tanks. We use this deck box for docks lines and small LPG tanks now.

136259
 

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I suppose a once per year long drive to fill is no big deal. However, I find we all accept a few of those rationalizations, until they eat us up. You either need a vented locker, or to mount propane on a rail. Otherwise, conversion isn’t too hard. Assuming your range has each orifice type available. The tank connections are easy. Captain's choice. I’d convert, it’s only getting harder from here.
 

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My system has a solenoid switch but what is the monitoring? I would think it’s more important to monitor propane which is heavier than air and can collect in the bilge and other low areas.
We have a carbon monoxide detector and a propane gas detector in Haleakula


 

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Discussion Starter #13
Yep, it's over for CNG in NE.

We'll limp through this season with one CNG tank and a propane burner that we found which fits nicely on the stovetop. That plus a propane Magma grill which is quite versatile we're finding. We steamed two lobsters on it last week nearly as fast as a stovetop burner (not to mention all the water vapor kept outside).

I've been eyeing the benefits for next season:

A 5-pound propane tank which takes up an 8" X 12" space, holds 107,955 BTUs.

Regular (not the longer-larger volume tanks) CNG tanks yield a "20-hour burn"; which they rate using a 4,000 BTU burner running for 20 hours(perfect world - in reality, I bet all fills vary of any gas).

An apples to apples comparison shows the LPG 5pounder will yield nearly a 27-hour burn.

Two LPG 5 pounders should yield 54-hour burns which means nearly equivalent to 3 CNG tanks. These days, with two onboard for more than a month, we'll use 2 CNG tanks for the season.

10 pounds of LPG will be more than ample. Why go to a bigger tank?

Further, the volume for the two LPG tanks, if you have to build a locker, will need a vented locker about 10" X 17" X 13". Compared to my two side by side CNG tanks in a rack that is about 12" X 20" X 24".

The little tanks will be easier to haul weighing about 10+ pounds full compared to CNG tanks weighing,... 40 pounds?

And of course, the savings for me in the above would be enormous as we're paying about $90.00 USD per CNG exchange here in mid-coast Maine.

So there's a look at the bright side of going from no-kaboom to BIG KABOOM!!! 😂

Just kidding. We use propane onboard and at home and are familiar with the slight added risk onboard.

My problem so far is locating the conversion parts for our CNG burners. I have this winter to sort that out. The rest is straight forward for us.

Working with a friend who will have to locate a vented locker below decks. That's the tricky part. I suspect there will be quite a few conversions next season unless something changes.

We're lucky to already have a space above decks with plenty of room for two, even three 5 lb LPG tanks. We use this deck box for docks lines and small LPG tanks now.

View attachment 136259
That is a lot of good information there. I appreciate the homework you have done on the size and capacity of the tanks. Didn’t consider that I might get by a couple of smaller tanks. We don’t do a lot of long distance cruising so a large capacity is not a big need.
 

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Discussion Starter #14
We have a carbon monoxide detector and a propane gas detector in Haleakula


Where did you locate the propane detector?
 

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The auxiliary one is in the bilge.

Also the two sensors for the solenoid are in the Vented propane locker near where the thru bulkhead fitting is located. The second is behind the stove / oven at ankle height.

 

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Discussion Starter #16
As it might become necessary for me to convert from CNG to propane I was exploring potential locations to put a propane locker. My CNG tanks are located in a space between the hull and pilot house that is accessible through a vertical hatch. The space may be large enough to hold a LPG locker.

I noticed there is a relatively recent regulation that LPG lockers need to be accessed through a horizontal hatch. Anyone know if going through a vertical hatch to access a horizontal hatched locker would be an issue? I might need to enlarge the vertical hatch to do the installation
 

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I'm not familiar with the vertical vs horizontal hatch rule. It stands to reason that a door opening from the side would not contain a heavier than air leak, as well as one that opens from the top. These rules are not always enforceable either, but that doesn't mean the point should be ignored, even if that's the case.

What makes abundant sense is that a propane locker should have drainage at the bottom that vents overboard. Often simple to do.
 

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Getting back to the CNG issue, the local Airgas folks told me that the Providence Airgas site (former Corp Bro’s. site) will fill tanks that are in certification (same periodic hydro test required as steel SCUBA tanks).

I’ve also heard from the nearby marina that recently handled CNG tank exchange that the CNG fill pump operated by Corp Bro’s had been down. They were waiting to hear what Airgas was going to do with this business line.

So the CNG issue is not dead. Years ago I got a refill at a Florida gas utility and, given the increase in CNG for transportation (buses, trucks) it would appear that there are options yet to be explored if Airgas doesn’t fully support marine tank refills/exchanges.

My boat has 2 80 cu ft CNG tanks and I will be pursuing this issue further with Airgas and other methane (CNG) sources, as appropriate. I feel strongly about preserving the use of CNG as a safer marine gas than propane.
 

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I'm interested to hear of your findings. I'm in the purchase process of a boat with CNG tanks and I'm not all that familiar with CNG. I do have a CNG fill station (for cars and trucks) near me so I'm exploring the adapter route.
 
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