Sealine 365 fuel tank leaking

[boat193]

Hi has anyone had problems with their Sealine 365 fuel tanks leaking diesel in to the bulge, both of the tanks on my boat have started to leak fuel into the bulge, the Forwarded tank is more or less impossible to access, but the aft tank I have opened up but inside it looks in very good condition. I know the boat is over 30 years old, so the tanks have done very well, they are aluminium, any information on where look for problems would be appreciated.

 

[Greg2]

It would be worth asking on the Sealine Forum

Aluminium tanks can corrode so there may well a leak in the tanks but worth checking if there are any drain plugs that might be leaking. That said it is probably unlikely that there are as they aren’t commonly found on Sealines (I say that as a previous Sealine owner). As an aside I always liked the 365

 

[Momac]

Probably corrosion at the base of the tank. Replacing the tanks is the best option although repairs may be possible.

 

[oldgit]

A not uncommon event unfortunately and can think of several boats including Princess/ Fairline and Sealine (a 42/5) which have suffered from this problem.
Usually involves engines out and replacement to remedy,am aware of a couple of other successful in situ repair jobs that seem to have lasted.
It would appear that Stainless/ Mild Steel / Aluminum all fail for different reasons.
In the case of a Princess 410 the owner removed both engines and replaced the non leaking tank at the same time.,
The boats were from the late 1980s to the early 1990s, failure seems to have been be after about 25-30 years.

Had two tanks fail, one in horrid nasty American Regal sports boat, the aluminium tank bottom corroded out due to bad design , tank was directly lying on top of boat ribs with fabric strip between bottom of tank and ribs.
Fabric was permanently wet and the alloy corroded, dumping all the fuel (Petrol) in the bilge. Tank could only be removed via a grinder as had been more or less bonded in to boat structure.
Other tank was a mild steel water tank buried under the side decks of a Princess 33, it simply rusted and weeped ,previous owners had bodged various fixes along the seams.
Only way to get it out was to literally cut it up with a grinder into small enough bits to get it out past the engines.
The tank had been covered in panels of a black foam insulation also in the final stage of disintegration.
It was replaced with a generic plastic tank at very small fraction of the price of a custom made stainless tank.
The fact that it was rigid plastic but with a little bit a flexibilty helped enormously when it was "encouraged" with a boot to go past the engine.

 

[simonfraser]

'the aluminium tank bottom corroded out due to bad design , tank was directly lying on top of boat ribs with fabric strip between bottom of tank and ribs'

nightmare - engine swap is 'better' imo

 

[Elessar]

Hi has anyone had problems with their Sealine 365 fuel tanks leaking diesel in to the bulge, both of the tanks on my boat have started to leak fuel into the bulge, the Forwarded tank is more or less impossible to access, but the aft tank I have opened up but inside it looks in very good condition. I know the boat is over 30 years old, so the tanks have done very well, they are aluminium, any information on where look for problems would be appreciated.

I had an S37.
A stainless rivet had fallen into the tank.
Everywhere it stopped it caused corrosion. Just a bit. It’s a big tank so was fine for 20 years.
Eventually the bottom of the tank turned into a teabag.
I took the tank out, had a new bottom welded on and a pressure test done.
Unfortunately taking it out involves collateral damage. I had to cut GRP to get it out and then fix it back in. I was sure the tanks were the things they built the whole boat around.

The tank is not going to heal you are going to have to bite the bullet.

Get rid of the smell with cats piss stink remover from a pet shop. Enzyme based it eliminates rather than masks the smell. Works on all organic smells including diesel and holding tank leaks.

 

[Elessar]

'the aluminium tank bottom corroded out due to bad design , tank was directly lying on top of boat ribs with fabric strip between bottom of tank and ribs'

nightmare - engine swap is 'better' imo

I don’t see anything wrong with the design in that regard . If it was an error as you suggest it would corrode from the outside in. Mine corroded from inside out.

The design error is having no thought to replacement/ maintenance.

 

[oldgit]

Eventually the bottom of the tank turned into a teabag.
I took the tank out, had a new bottom welded on and a pressure test done.
Unfortunately taking it out involves collateral damage. I had to cut GRP to get it out and then fix it back in. I was sure the tanks were the things they built the whole boat around.

A distinct l' odeur du Rouge when viewing any prospective boat purchase could just be down to years of careless fuel filter changes.
Apparently skippers of old wooden boats appear to think it increases the charm of the things.
Well remember being invited on board some old classic motorboat and trying not to inhale while aboard.

Have viewed boats where the owner appears to think that the bilge under the engines is the ideal place to store years of old engine oil/diesel plus cable ties dropped nuts and bolts and other gloop.

The whiff of diesel should ring alarm bells on any modern glassfibre boat, fuel tank weeps are almost impossible to dectect visually if the seller has been "clever" in cleaning bilges and good chance the buyer will not find out of the problem for quite some time.
It will take time and money to trace and repair.
.
.

 

[dj43]

Mechanics will say engines out, but if your hands on take out the furniture lift the floors to access the tanks, either way not an easy job , done this on F43