35.5 Conversion from CNG to LPG

[BLIGHT]

I own a 1989 model 35.5 Legacy and intend to convert to CNG from LPG. I already have the necessary stove/oven conversion kit so that is not the problem. The guestion is how and where to run the gas hose to reach the Port locker on the swim platform. In my "89 version the fuel tank was installed behind the aft stateroom on the port side on a platform. As owners of this series know the mounding of a tank on the aft rail is very limited just do to the limited area so, that is the reason that I have chosen the starboard aft swim platform locker as a location for the LPG storage locker. Any help would be appreciated.

Bob

 

[weinie]

I believe the hard part is that you are going to need ventilation at the lowest point of your locker. You don't want fumes to seep into your bilge or cabin nor do you want your locker to fill up with sea water. Remember CNG rises... LPG sinks.

 

[BLIGHT]

Thanks for your input but I intend to have a bottom drain on the storage locker that will drain overboard and located lower then the storage locker.

 

[Alan]

Based on the discussion I'm thinking you want to convert to LPG not CNG. I would run your hose under the bed in the aft compartment. There are access lockers there to make the run easy. Once you're in the compartment behind the bed you will have access from the bottom of the cockpit locker. If you don't already have an access hatch in the bulkhead behind the bed you can easily install one in that bulkhead.

 

[MetricMountie]

CNG to LPG

Alan

Have you converted your 92 to propane, I've got a Liberty Cup Edition as well and I plan on doing the conversion but I'm going to mount the tank on the stern rail then install low pressure hose through the stern below the combing level then through both the swim and inboard port lockers, then under the bed to the stove. Do you foresee any problems with this route.

 

[BLIGHT]

Thanks Alan and yes I'm converting to LPG. I was checking the pan that the fuel tank is installed on and I guess that I have to drill an access hole through that pan in order to gain access to the locker under the bed in the aft stateroom. In order to do that I assume that an access hatch should be cut in that bulkhead, or find a very small person to lower into that area to cut the access holes.
Thanks
Bob

 

[stuart.hamer]

I too have a 35.5 although mine is a 94. I love the CNG and would not consider changing although I understand CNG can be hard to find in some places.

As for the location I would be concerned about heeling over and water potentially coming in through the vent if the tank is in the starboard swim step locker. Are you sure this would not be an issue?

For the hose I assume you have a current hose for the CNG that goes to the port side cockpit locker. I haven't traced this but I imagine it goes under the bed. It may be possible to reuse it or at least reuse the routing from the back to the galley.

Stuart

 

[PJ]

I would have to agree with Stuart. We have CNG on our 90 35.5. I would never convert. I do understand finding a place to fill CNG tanks can be a challenge. I found a local (50 miles away) school bus company that runs there buses on CNG. They fill my tank for $5.00. We live on the boat for about 1 month and daysail the rest of the season until the water gets hard. (We live on Lake Michigan). A tank lasts us 3 seasons.
Try this link for a fill site near you.
http://www.afdc.energy.gov/afdc/fuels/natural_gas_locations.html

 

[Alan]

I still have my CNG system and one spare tank which I keep full. I would much prefer to keep the CNG over the LPG. As a safety factor CNG is much less hazardous and storing the tank below decks is the best alternative. With two tanks I can get through a season and do the refill in the off season.
Running the line for LPG through the aft stateroom under the bed and up through the aft lockers should be fairly easy. Access hatches can be installed with relative ease. When I changed the plumbing for the head and holding tank I was able to get my sons girlfriend into the aft cockpit locker to help with these cramped quarters. She had little trouble in there and was enormously helpful. I now have PVC plumbing for the head which should make future hose changes (smell issues) completely unnecessary.

 

[MetricMountie]

CNG to LPG

As indicated in a couple of the posts, CNG is hard to get in many locations in my area it is next to impossible. The closest location is via exchange at Hinckley Yatchs in Maine which is still a long drive from our home port. I exchanged my two tanks there this past August which cost me $70.00 a tank for as what was mentioned previously about $5.00 worth of gas. On arriving home and connecting the tanks we found the tank pressure to be less than 1400psi which is less than half the capacity of the tank. Hard lesson learned and too far to return and complain. LPG is our only out.

My wife and I use the boat every weekend from May thru October plus our usual two week coastal cruise and use the stove top and oven daily. Additionally we are installing a Dickinson LPG fireplace in the spring. Though I understand the safety issue around LPG vice CNG we really have little to no options.
I'll be taking Alans' advise and routing under the bed via the aft lockers. This route is not a problem as on purchaising the boat we had a major problem with the rear cabin bulkhead which was susequently removed and replaced by a two piece unit which is readily removalble allowing access aft with little problem and plenty of room. Thanks to all for the posts.

 

[BLIGHT]

Re: CNG to LPG

To answer a few questions, the main reason that I want to change to LPG is the cost of CNG in my area is now running about $85.00 per exchange and that is if the tank is within the time limits of recertification. I believe that to be 5 years, if not, add another $20.00. My wife and I spend most weekends on board plus a few weeks for cruising during the summer months, so going through 2 tanks of CNG is not hard for a season and we don't even use the oven. Yes, CNG is a great product if the cost of exchanging tanks would be more in line with the cost of the gas. A few years ago I had the use of an adaptor to fill the tank from several CNG outlets located at gas stations in the area and the cost per refill was about $1.00. Needless to say they are no longer in operation. As noted in PJ's link to CNG refill stations, Maryland has none that are open to the public they are all either private or government usage only.
To answer the vent drain question I'm planning on venting the locker overboard just above the waterline on the port side, yes when sailing it might be below the water line for a time but, not that far below that the water should enter the locker through the vent hose. Even if it did it would drain when the boat is upright. In my "98 35.5 the CNG tank is located in the salon under the seating area on the port side. I have also found that you can't use the CNG hose for the LPG and purchasing a 1/4" rated LPG hose is very inexpensive.
I have also found out that Seaward, several years ago made a batch of conversion kits for their stoves and ovens but, they only made so many and now the conversion parts for the oven controller are no longer available. There might be a chance from what I have heard that some newer stoves have the correct controller that contains a switchover setting. The place to check is todd@suremarine.com Seaward does manufacture a Tank Locker that contains a 1 gallon tank that is relatively small in size that could be used in a small area. Please note that with LPG you should either install a Tank Locker with a vent drain or mount the tank on the outside of the vessel.
Bob