People are converting to propane. CNG is on the way to disappearing as the fuel of choice aboard small boats as portable tank filling stations are being closed. Boaters have just been using an insignificant amount of CNG and it does not compensate for the costs of having portable tanks filling stations. CNG is stored at much higher pressure than Propane and the tanks and filling equipment are also more expensive. Moving on, the boating industry has devised a safe way to handle propane and it incorporates the use of thermocouple switches in propane stoves, enclosed tank lockers vented overboard, remote gas shut off solenoid and pressure switches, gas fume sniffers and other safety items that add up to $$$ for a by the book conversion. If you want or need to carry insurance on your boat a full propane installation will be necessary in order not to forfeit coverage. Like everything in our lives today the industry requirements are an attempt to make propane use more user friendly, idiot proof and perhaps safer.