Propane is heavier than air so it will sink into the bilge if given a chance. There are lots of opinions on how best to rebuild your system, but it's critical to educate yourself, don't rush, test everything (and retest often), and only take expert advice.
Our original stove was looking pretty sad. We had not used the oven in years so the decision was easy to simply replace the old 4 burner stove top with a new Force 10/ENO 3 burner unit. The oven is completely disconnected from the propane and electrical, and only used for storing pots and pans and makes a good faraday cage for electronics during the occasional lightning storm.
During my annual check I discovered a crack in a propane compression fitting. It was not leaking (yet!), but nothing is scarier on a boat than a propane leak. Since most of the components were original, and I have no desire to enter the annual Darwin Awards, it was time to replace the complete system. ABYC standards have also changed since 1972 to require an uninterrupted supply line from the propane locker to the stove. My original line was copper, with a short flex hose at the stove to accommodate the gimbal. This was out of current code so out it came.
I was able to take the old stove top, remove all the old propane burners and cut out all around the burners. This created a sold foundation to drop in the new unit.
The 16 feet long copper line came out in 8 pieces. The flex hose was another 18 inches. A new, 18 foot one-piece braided hose with swaged flare fittings was ordered from Sure Marine. So was a new solenoid, regulator, pressure gauge, fittings and 2.5 gallon tank. All parts and pieces were packaged and ready for pickup in 3 short hours.
TEFLON TAPE
One of the important learnings from this experience was the proper use of PTFE yellow teflon tape. White teflon tape is for water fittings, is thinner and does not resists degradation from propane. Yellow teflon tape is thicker, and is NOT used on compression fittings. The connection is made inside the flange fitting, not by the threads. If you use tape on the threads then the compression fitting cannot mate and seal properly. The only place to use yellow teflon tape is on non-compression fittings.
The main purpose of a thread seal tape is to seal out micro abrasions or surface irregularities on threads. If you have a major gash or nick on a thread, you will need to replace the pipe section or re-thread it, rather than applying a thicker seal tape layer.
Minimize your clock-wise turns around threads. Only add more than 3 if you're trying to align a component properly. Don't over tighten!
TANK
Steel propane tanks are required to be inspected every 12 years and every 5 years thereafter. I went with the only tank that fits my low-profile propane locker, a 2.5 gallon tank. This same tank worked well over that last decade and only needs to be refilled onece a year. Since it's steel, and it will be exposed to plenty of salt air, rust is not its friend. To keep it off the bottom of the locker floor and away from the inevitable corrosion, I used an old fuel line and split it down one side. I then pressed it on the foot of the tank and added a few dabs of silicone to ensure it doesn't inadvertently slip off. The tank weighs 20# full.
PRESSURE GUAGE
A pressure will not measure of tank volume, but it it good for checking for leaks. A pressure gauge only informs you of the internal tank pressure, which changes with air temperature. Weigh it with a fish scale to determine how much propane you have in the tank.
To test for leaks, turn on the propane tank valve but not the solenoid. The line up to the solenoid will pressurize. Then turn the valve off at the tank and wait at least 3 minutes. If the pressure decreases, you have a leak. Locate the leak with soapy water and a paint brush and look for bubbles.
When I first installed this gauge the ambient temperature was 70° and the new tank the pressure guage read 125psi. Later, at 57° the tank pressure gauge read 105psi. Air temp has a direct correlation to tank pressure.
REGULATOR
This is a low pressure regulator that reduces 125psi to .44psi.
SOLENOID
This is a low pressure solenoid thats circuit is actuated by a switch on the electrical panel which can be easily accessed from the stove.
SUPPLY LINE
Braided, marine grade 3/4" OD. My line is 18' long and in one piece from locker to stove. I added rubber grommets to reduce chafe where the hose passes through the bulkheads. This also creates a airtight barrier in the propane locker.
TANK TIE DOWN
Still got some work to do!
LEAKS
Once the system is intact, testing for leaks is absolutely crucial. As with all plumbing, you never want to over tighten a connection as it could crack the fitting. I like to thread the fitting on by hand first to ensure there's no cross threading. Then tighten the fitting as much as you can by hand. Then use tools to snug up the fitting by tightening 1/8 - 1/4 of a turn. Cracks in fittings that have been over tightened can appear over time due to vibrations. A bit too loose is often best to start out with, then tighten incrementally to stop any leaks. Most of this is done in the propane locker but also check the compression fitting connection at the stove.
- Your nose is going to be the first indication of a leak.
- Soap and water dabbed on with a paint brush will help you pinpoint any leaks with a bubble stream.
- Opening the tank valve then shutting off the valve will pressurize the system. Watch the gauge for at least 3 minutes to see if any propane escapes. My first fill indicated 125 psi. If the pressure goes down at all over time, you have a leak. It's best to check this every time you use the stove.
REFERENCES
This is one project you'll want to read everything you can. If you're in the Seattle area Sure Marine is a excellent resource for parts. I spent a fair amount of time picking Graham's brain. He is sharp and teaches at the Northwest School of Wooden Boats. He is also quoted in the NW Yachting article below.
