do you know the type number of your D5W?( read from the heater dataplate). We ought learn this, so we fully understand what heater model you have currently in your narrowboat

This upgrade kit includes a wiring harness and controller so yes it certainly could be used to update your old heater. I think it sensible though that you check your existing exhaust system for gas tightness and worthiness prior installing this heater as you will need to re-use this, also the combustion air pipe.

Also check your fuel lines, with a Narrowboat installation they should be copper fuel lines and a compression fitting possibly at the heater. This connection is probably best redone with a 50mm long ISO 7840 Fuel hose connector.

Let me know, if you have any further questions please just email sales@butlertechnik.com

Thank you