[C320-list] Leaking Tank Problem

[Jeffrey Kapec]

I had discovered this problem very suddenly (quite 
unexpected) and it created a huge mess.  My 320 is 2000 
vintage.  Two years ago, on the day we were about to bring 
the boat in for the fall haul out at the end of season I 
smelled a distinct oil scent on the dock as we approached 
the boat.  When I opened the companionway the smell was very 
intense.  I knew what that distinct smell was from. looked 
into the bilge and there was about 2 gals of diesel in the 
bilge. Ayyyy.  Checked all engine fuel lines and everything 
was tight and dry.

There was no previous scent or indication of leaking fuel; 
we are on the boat several times a week during the  entire 
season so we would have noticed something slowly 
developing.  Made a quick diagnostic check where the tank 
may be seen from the port side inspection hatch in the berth 
and found that the tank seam 3/8 up from the lower right 
corner was leaking one drop per 30 seconds.

Had to take the boat for the haul out that day, no choice, 
with 3 hours motoring point to point we had to clean the 
bilge and try to reduce the rate of leakage.


Made it fine but clean up and odor elimination was very 
difficult.  Vinegar, vinegar and then dish detergent 
solutions.  A few days later the boat is up on jack stands.  
Extracted all of the fuel out of the tank by taking the feed 
line that attached to to the Racor, attaching a line to the 
end of that feed fuel line , disconnecting the cooling 
intake hose nearby and running the temporary drain hose 
through the open seacock. So now, I have a hose sticking 
outside the hull through the raw water intake .  Now outside 
under the hull, placed the end of that temp drain hose in a 
series of large containers..... after achieving siphon 
action the entire tank drained quickly.

John Vez offered some very useful / helpful information at 
this stage  given that he had the same problem.

I removed all of the tank fittings and attachments and then 
removed the tank through that very inspection hatch in the 
berth. You have to remove the frame and hatch as well.  Only 
then will the tank fit through that opening.

The padding under the tank is spotty and questionable.  
There may have been contact with moisture enabling galvanic 
action.  It appears that the seam was compromized over time 
but again only a small crack.

I bought a thick rubber mat that is used for standing on 
concrete shop floors and cut that down to fit the foot print 
of the tank. This raised the tank one inch from hull 
surface. All rubber complete isolation.  I then replace the 
tank.  Some folks recommended a cheaper welding repair, 
which was possible, but I did not want to take any chances.  
Everything is fine now.  The new tank was not cheap.  Some 
mechanics are now recommending that you drain the diesel  
fuel from the tank every fall. Really?

Jeffrey Kapec
Petite Suite Hull 718