Assuming you have a double skin chimney, I solved that one by filling the space with fire resistant spray insulating foam - about a tenner for a can. You can only use the can once - and I reckon there are several chimneys worth in the can - so maybe share it.
Trim the excess with a knife so it matches the flue pipe on the boat. Charley Once you have used the spray foam you need to hold the can upside down and press the trigger. This clears the nozzle and allows you to use the foam at a later date John nb Charlotte Rose .... this works for any spray can where the contents can dry up or harden [Non-text portions of this message have been removed]
