Sagging fuel tank causing water to get in the fuel?

[mlrman]

Any help would be appreciated!

The Sunbird is in the shop again after having the sending unit replaced last year. The shop is saying there's water in the gas again due to the new sending unit becoming corroded like the last one, due to a sagging gas tank. They are saying they can't patch it, and it needs a new fuel tank, which they aren't willing to do because the floor will need cut out.

I don't understand how a sagging tank can cause this, especially when I always keep the boat under a full, vented, sharkskin cover. He it can happen from condensation, but when he drained the tank last time, he said it was like 50% water.

Honestly, I'm not sure it's worth paying another shop to cut up the floor and put a new tank in a 20 year old $2500 boat.

BTW, it's a 91 Sunbird Corsair 198 cuddy cabin with a V6 OMC if that matters. Thanks!

 

[alldodge]

Don't think its the sending unit, water an aluminum do not play nice. If water stays against aluminum, it will eat holes thru it. This is why many folks don't want to foam in tanks, but the issue is if water gets into the foam.

My 95 Formula almost had a leak before replacing the tank, and the aluminum water tank caused the leak years before I got to the fuel tank. I'm in fresh water, and slat is even worst

 

[Scott Danforth]

Cut the floor out, drill the stringers. If youre lucky, only the tank needs replacing and the floor patching. If not, the whole hull may need restoration

 

[mlrman]

Don't think its the sending unit, water an aluminum do not play nice. If water stays against aluminum, it will eat holes thru it. This is why many folks don't want to foam in tanks, but the issue is if water gets into the foam.

My 95 Formula almost had a leak before replacing the tank, and the aluminum water tank caused the leak years before I got to the fuel tank. I'm in fresh water, and slat is even worst

Well they replaced the sending unit once already and are saying it's corroded again due to the water?

What aluminum part are you referring to? I think my tank is plastic.

I'm in fresh water. Thanks for the response

 

[mlrman]

Cut the floor out, drill the stringers. If youre lucky, only the tank needs replacing and the floor patching. If not, the whole hull may need restoration

The floor and stringers are solid as heck! This boat never sees rain and is always covered if not being used. I've talked to other shops that don't see how a sagging tank with a proper gasket around the sending unit access would allow that much water in the tank.

 

[Scott Danforth]

test drill before you make statements about a 27 year old sunbird stringers.

as for the tank, pop the hatch and look at the tank. only way water can get into a tank is if the tank is submerged and getting in from the sending unit, the tank is corroded and has a hole down low or its coming in the fill cap and vent.

so either you have water above your tank level in the bilge, your tank has a hole or two in it or you have a vent or fill cap issue.

 

[Bondo]

Ayuh,...... Sunbirds are entry level boats,.... for whatever reason, the sender is always wet, 'n corrodes,....

Have another unit put in, 'n have 'em Slather the whole thing with a fist fulla Grease,....

Ya might get 3 or 4 years, rather than 1,....

Of course, drainin', 'n ventin' the cavity would probably do wonders,....

 

[Old Ironmaker]

That must be a load of water to get to the sending unit of which I'm thinking is at the top of the tank, where's all this water coming in from? My sending unit is on the top of the tank just below the screw down hatch. Outboard StarCraft. Where is yours? I would be leery of putting much money into a 27 year old 2500 buck Sunbird, with a dreaded OMC no less. Good money after bad and all that?

 

[ahicks]

I've seen the issue he's talking about. The top of the plastic tank is sagging as the only support it has is around the sides, and of course the sending unit is located right in the center of the top. ANY moisture, from wet bathing suits or whatever, that drip on to that tank, will collect at the sending unit. Sending units are often not sealed all that well, and will allow the moisture into the tank.

 

[alldodge]

Plastic, ok

 

[mlrman]

Ayuh,...... Sunbirds are entry level boats,.... for whatever reason, the sender is always wet, 'n corrodes,....

Have another unit put in, 'n have 'em Slather the whole thing with a fist fulla Grease,....

Ya might get 3 or 4 years, rather than 1,....

Of course, drainin', 'n ventin' the cavity would probably do wonders,....

Yes, this is what I'm going to do. And have him vent it. Like the other poster said, it's not worth putting that kind of money into this old girl. Thanks, this forum has always been very useful for me!

 

[mlrman]

That must be a load of water to get to the sending unit of which I'm thinking is at the top of the tank, where's all this water coming in from? My sending unit is on the top of the tank just below the screw down hatch. Outboard StarCraft. Where is yours? I would be leery of putting much money into a 27 year old 2500 buck Sunbird, with a dreaded OMC no less. Good money after bad and all that?

I hate to say it, but I think you are spot on. It's been a great first boat, but it's just not worth cutting up the floor, replacing the tank, then hoping nothing else major goes wrong. I already had the ole' OMC gear oil change fiasco before I started doing my own maintenance, where the shop didn't fill it properly and she locked up. Luckily, I found a used drive for $500. Score!
The motor runs great but who knows how many hours are on it. It's still a solid, fairly clean boat though, so I hate to just part it out.

 

[Old Ironmaker]

I feel your pain. I had to park my wife's 2007 Nissan Altima this winter with close to 400,000 kms on it with a bad tranny, looks mint, not a scratch on it, looks are deceiving.

 

[mlrman]

Yeah that's tough man!