Thanks for the replies.
I purchased the boat from a mate who downsized to a smaller boat. He said that when new it read full but after some time it never read full again, only around 3/4 or a tad over.
I agree that the only way to tell is to take it out.
How accurate can they be anyway? From the top of the tank down it is rectangle for 50 mm then it becomes a v shape.
I can understand that if the tank was rectangle from top to bottom then the float would be say reading half full when the fuel level was half full, but in this shape tank if the float was at the half way mark (overall height) then you must really have less than the claimed 65 litres it is supposed to hold.
I don't know what the gauge reads when empty as I have never drained it.
I spoke to a dealer today and they said to remove it so that they would be able to order the correct replacement. I thought that may be the only option.
Thanks again.