Below deck tank replacement ! HELP?!

Liammcgee123

Hi , Basically I have a 5.1 meter redbay rib with a below deck fuel tank (roughly 60l) that I want replaced . Every season I have the same problem over and over of water in the carburetors. Recently I rebuilt the carbs , installed new fuel line, bulb and water.s. I added stabill for stabilizing the fuel and still water appears in the filter and carbs !

I checked the fuel lines again and air vent on the tank but it has to be the tank ! I even emptied it recently through the hatch... (I’ve lost all faith in marine mechanics as I found rubber from a welly as a gasket )

***Therory***
It’s a plastic tank and I suspect it has a minor hole or crack the only opens when the boat in in rough weather ... the tank flex’s I’d imagine ! (Water enter from the what’s in the hull)

How do I replace it ? The centre console isn’t screwed on but stuck on .. I don’t know what glue and material it is ? It’s like a white strip around the bottom .

I recently got a quote for €2200 which is crazy ! They said this involves adding a new console , cutting the deck and adding anti slip . Obviously just creating work to make a few euro !

Any help I’d really appreciate! Thanks

gctest50

Put a floating fuel pickup in it and see if it helps

Liammcgee123

gctest50 wrote: »

Put a floating fuel pickup in it and see if it helps

Yea there is one in the tank already

fergal.b

If you have an inline water separator just before the fuel gets to the carb you should be able to see the water in the bowl and drain it before you start the engine. It would be hard to tell you how to remove the tank without seeing it, maybe try draining the tank and then pressurise it with air to find and repair the leak. Another option might be to use another tank and see if you are still getting the same problem it might even down to where you are getting you fuel that causing the problem it wouldn't be the first time I have heard of a place selling fuel with water in it.






.

spaceHopper

But in a filter and dewater, the fill the tank completely after each trip, if you have an air gap and damp air you get condensation forming in the tank. If the tank is full, no gap no air no water.

sogood

Yes to all of the above. A step by step process of elimination is needed. Do a pressure test on the tank. Fuel gauge sender gasket/seal can be a culprit as can the vent line taking in water while underway. It should also have a loop in It, like a "U" bend on a toilet.
As mentioned , without pics it's hard to formulate a removal procedure.

Liammcgee123

sogood wrote: »

Yes to all of the above. A step by step process of elimination is needed. Do a pressure test on the tank. Fuel gauge sender gasket/seal can be a culprit as can the vent line taking in water while underway. It should also have a loop in It, like a "U" bend on a toilet.
As mentioned , without pics it's hard to formulate a removal procedure.

Yes you’re on the right track definitely! The previous owner took it to Redbay for examination. They removed the fuel , filled the tank with water , waited 1 day before saying “nope you’re tank is ok” I’ll not be going to them in a hurry ! As for the gasket I’ve sealed around the top with chemical resistant sealent (resists petrol.. I checked). There was always air getting in at this point and I noticed a small pinhole still here ! But surly that wouldn’t cause the water if it’s hidden under the console

sogood

Liammcgee123 wrote: »

Yes you’re on the right track definitely! The previous owner took it to Redbay for examination. They removed the fuel , filled the tank with water , waited 1 day before saying “nope you’re tank is ok” I’ll not be going to them in a hurry ! As for the gasket I’ve sealed around the top with chemical resistant sealent (resists petrol.. I checked). There was always air getting in at this point and I noticed a small pinhole still here ! But surly that wouldn’t cause the water if it’s hidden under the console

Boats, by their nature tend to be wet. Water gets in under gunwales, between the cap and the hull and it makes it's way back and down, dictated by science and the forward motion of the boat in a slightly planing attitude. Where it eventually gets to is infinitely variable. Even without water ingress you can have condensation, which can form inside your fuel tank, so being below deck is no guarantee of a dry environment. Possibly quite the opposite. Do you have a seal/ "O" ring on the filler cap and if So, is it intact?
As mentioned, some pics might help with a diagnosis.

Daibheid

If you had a crack or hole in the tank you'd probably have a very strong smell of petrol if not actual petrol sloshing around in the console. The fact you know you had a seal issue could easily be causing the problem with contraction and expansion every single day bringing fresh moisture laden air into contact with cold fuel.

I would never contemplate using a boat with an internal tank that doesn't have an in line water separating filter. Becasue you'll get water building up from condensation anyway - more so with a metal tank- or as Fergal pointed out, you could be buying water. If you're fitting an inline filter try get a transparent one so you can see the water before it gets to the carbs.

Another point to note on internal tanks is it's good practice at the end of the season to either empty them completely or fill them completely to minimize that air gap above the fuel where you'll get condensation.