Most 'gas' suppliers and gas appliance distributor outlets can do this for you ... and also adjust the burners for the proper air/fuel ratio. Best is to remove the entire stove and take it to them for the conversion and set-up adjustment if youre not completely knowledgeable with CNG/propane regs. as many of the 'regs' have changed over the years:I think you just need to replace the oriface. Contact Sure marine in Washington state