Is the smell noticeable stronger when boating, or always the same?
If it's smelling like fresh gasoline then it's a leak somewhere, kind of faint/stale fuel smell could be old hoses transpiring but it's a different smell.
My 30ft RIB had for a year, fresh fuel smell in bilge but no leak could be found, nor fuel sheen in bilge water. After it became worse i decided to pull the cover and could see nothing so we pulled the tank and found the culprit. A almost invisible pin hole on the lower stern tank wall and only visible by a faint humid spot.
My BW 23 Outraged developed pin holes as the tank was sitting so low that it touched water if tank and bilge was full, but as it corroded from outside they were visible.
As you know that fuel vapours are very dangerous i suggest to
1° check fiel level sender plates, a momentary dry fuel leak is visible by colour change
In this case you may reinstall the fuel sender/s using a new gasket
2° Pull the fuel tank cover to have better view to the tank and hoses
3° last resort is to pull the tank and then replace it, 27 years is a respectable age for a fuel tank.
Same for all fuel hoses and probably senders too, thats the cheapest part of the repair and you don't want to do it again after a few years as another problem arises.
When you do a search you find contacts from companies who will build you a new one, out of the shelf tanks may fit, but in case will reduce fuel capacity considerable, so a to measure built one is the only solution. A repair may sound financially attractive but i would not repair such a old tank.
Chris
