View Full Version : BIGGG Fuel Tank Problem
steveg1100
17-09-2006, 02:53 PM
Was going to go out fishing this weekend. Headed down South to my parents house were my boat is kept. Decided to give the boat a once over. On pulling out one of the bungs fuel starts running out. (should point out boat is a sharkcat) So I have a leak in one of the tanks. I will have to cut the floor up on one side to see what is going on. Has this happened to anyone else with a twin hull boat???
Any suggestions hints would be greatly appreciated.
finga64
17-09-2006, 03:47 PM
I think that has to go in the Ooh Oh category :'(
steveg1100
17-09-2006, 03:54 PM
Yeah Ive been pissed off all weekend.
steveg1100
17-09-2006, 03:59 PM
Thanks to seabug that sent me a message to be wary as the hull will be full of vapours.
No smoking near my sharkcat ok. Its better to laugh than cry.....
Steve, its going to be a drama having to cut up a floor just to get at the tank, but it maybe just as simple as a perished fuel line or stuffed hose clamp and not a hole in the tank causing the leak. Hope it turns out to be a simple fix and play it safe around that fuel, good luck ...foxy
Pirate_Pete_Tas
17-09-2006, 05:16 PM
A good way to make it safe whilst working is to hook a hose to your car exhaust & poke it in the bung hole & wait 10 min or so & fill the hull full of exhaust fumes........................Then cut open the floor. no oxygen = no bang
23-sharkcat
17-09-2006, 05:30 PM
the tanks in my 23' sharkcat are glassed in and the are no rubber hoses that go through the floor, only stainless steel.
the other thing is that the section where the fuel lank lives is fully sealed off from the other compartments. when I replaced part of my floor it was full of water and had to drain it out because of the fact that it was sealed.
I would be looking somewhere else Like where to fuel hoses come into the engine compartment.
steveg1100
17-09-2006, 05:51 PM
From what I can see there are no hoses going under the floor. There are three stainless pipes coming out from in the floor. A larger one that is used to fill the tank and two smaller ones one for the fuel line to the engine and the other to the breather. It is then above the floor level that the hoses attach with clamps.
Grand_Marlin
17-09-2006, 07:20 PM
G'day Steve,
Be very, very careful with this - it has the potential to kill.
Syphon out as much fuel as you can.
Fill the fuel tank full of water, until it overflows out the filler ... given that fuel floats on water, the remaining fuel should then be flushed out.
Most Sharkcats have the 4" screw in inspection ports for each compartment.
Actually, remove all ports on the one side to let it air out.
If it has, remove and fill with water ... you said the cat has bungs - this points to an early model cat, which may not have individually sealed compartments.
Flush as much of the fuel out as you can ... even if you have to do it a few times, then put the bungs in ... partially fill the hull, then rock it backwards and forwards with the car.
Drain and flush again.
If possible, fill the compartment full of water before you start cutting.
If possible, use hand tools, not power tools to cut out the floor - a hand saw (jack saw) will cut glass and ply.
Dont use power tools unless you are absolutely certain that there are no fuel vapours, and the only way to do this is hire a gas detector.
If you have some more info on the boat and pics would be handy.
Cheers
Pete
steveg1100
17-09-2006, 07:51 PM
Thanks for that info pete. I should have taken some pictures I won't be back down there till next week. THe boat is a 1980 sharkcat 5.5m. There are no inspection ports on either side so I can't really air it out or fill the cavity around the tank with water. In fact I'm not sure what I will find under their. I was going to drill a 100mm hole in to see what is below before cutting out the floor but I can know see that they may not be a good idea. This is getting worse and worse why couldn't I have a simple problem.
Darryl
17-09-2006, 08:18 PM
I'l swap you a v187 Caribbean Crestcutter for it.. ;)
Just kidding mate , not good news at all, especially if you haven't got inspection ports either to try and see what's going on. Watch the fuel vapours as people have said , especially if the hull cant air out at all.
Maybe a take it to the experts mate unfortunately.
steveg1100
17-09-2006, 08:57 PM
If I can drill by hand a whole big enough I can then use a hand saw to enlarge it enough to get a good look and get it to air out. Or maybe I can try the exhaust fumes like pirate pete suggested although I have never heard of this method before.
I wonder what has caused the tank to leak???
fishingrod
17-09-2006, 11:32 PM
There are pneumatic (compressed air) driven tools available. Maybe you can hire them?
They are inherently safe with no motor to generate a spark. The other danger that comes to mind is a spark from the cutting blade/drill bit hitting a screw or metal object.
steveg1100
18-09-2006, 09:12 AM
Thats a good idea I will have to drag my compressor down there. Could be handy for also blowing air through the hull to exhaust some of the fumes out once I have an inspection hole. I will proceed cautiously and slowly with this one. I really hate the thought of doing it because the cat has a good solid floor with very little wear and tear for the age. Once in there do you think it will be an aluminium or stainless tank.
Noelm
18-09-2006, 09:51 AM
I have cut the floor out of an old Sharkcat, you need to make sure you do not cut too deep, you will find that the floor is about 10mm think in total, and under it is a series of frames that actually are the strength, the floor only serves as a "walkway" if you get what I mean, the tanks are usually located with the filler pipe to the front end of the tank and the smaller pickup pipe is at the rear end, this will give you and idea of the size of tank, and it will have a few compartments under the floor, but unlesss it was built to survey (which yours isn't because it does not have inspection ports in the floor) they are not sealed and water/fuel can flow from one end to the other, the tank itself will be about 4 inches or so below the frames under the floor.
fishingrod
18-09-2006, 01:05 PM
Just an additional note re the pneumatic tools.
You still get HEAT coming from the from the saw blade or drill bit.
Obviously carefully disconnect and remove the batteies from the boat before starting anything.
And wear some wollen clothes. Not nylon that will burn and stick to you if the worst case happens :-/ Also you dont want static electricity on your clothing too.
And no mobile phones or any electrical devices near by.
steveg1100
18-09-2006, 01:39 PM
Thanks Noelm. It's good to hear from someone that has done it. On my cat the filler pipe protrudes from the floor about halfway up the deck and then there is a pipe coming out on either side of it. one is the breather and the other is the pickup for the fuel. The cat is a 1980 model which I think is the model just after the 560 series (correct me if I'm wrong). I wish I took some pictures while I was there.
Grand_Marlin
18-09-2006, 06:57 PM
G'day Steve,
The 560's were early to mid 80's ... yours is pre 560 series.
I have a pic of a 23 footer, floor removed - hope it helps... the 18's are constructed the same.
Cheers
Pete
Grand_Marlin
18-09-2006, 06:57 PM
another
steveg1100
18-09-2006, 08:29 PM
Grand Marlin your a legend. That looks like it even the filler hose for the tank is in the same location. The breather used to be in the same position as the picture but has being routed to the rear of the boat.
So the tanks are sitting under the bolted in cross beams I can see in the picture. Are they aluminium tanks in the boat?? If I find just a small pinhole and the tank is in good condition is it acceptable to use a product such as steel epoxy. They claim once cured is impervious to gas oil and alchohol.
I suppose I should wait and see what I find. I will want to make sure once I glass the deck in again that I will not have to go under there again.
Although I was thinking of putting in those round inspection hatches just so that you can have a look around under there. Peace of mind thing.
Thank you again for the picks.
Eagle
18-09-2006, 10:22 PM
Hi Steve
Just finished looking at your pictures and your story, not real good but take heart cobber. It wont be real hard to fix. One thing I wouldnt do is put the car exhaust into the boat and run the car engine. The way to go is to get some dry ice which is frozen carbon dioxide. I have used this to fill a petrol tank that had a bad leak. I stuffed all the outlets with rag and left one open at the highest position #in the tank. This last vent SPEWED out CO2 like a storm cloud. I was then able to OXY WELD the holes in the steel petrol tank. I strongly sugest you fill the cavity/s with CO2 before you do any cutting. Fill the fuel tanks with it as well. You will be amazed how fantastic this technique works. I would not fill the tanks with water, no way. Fill them with the dry ice (CO2), you only need about .75 kg of the stuff in a fuel tank to do the job. #To suck out any fumes, get an appropriate length of 20mm or 25mm hose and about #100mm from one end, drill a 6mm hole thru the side. slip a short length (about 150mm ) of 6mm copper pipe and lay the pipe back towards the far end of the hose. you need to have about 25mm of the pipe inserted into the hose and pointing toward the outlet end of the big hose. Connect your air compressor onto the small pipe and place the inlet of the hose (the opposite end) into the boat cavity or wharever you wish to suck out. #Turn on the compressor and let it run. As the air blasts out of the small pipe it will suck out all the air/fumes/water/fuel etc and blow it all away. This is a very efficient and safe way to clear all under the floor and from inside the tanks. Do this before you toss in the dry ice.
It looks like you may have to cut a section out of some of the floor frames. Dont let this faze you. Its easy to rejoin the part. Cut the frame on a long angle to make a scarf joint. Make the length of the cut about 4 times the thickness of the frame. Glue the section back in and use a couple of layers of 6 oz glass cloth soaked in a suitable epoxy to seal the joint and take up any irregularity in the cut. The glass will also pack the section out so the frame is uniform in its section again. Put a couple of stainless steel or bronze screws #through the joint to hold it as the resin cures. I would prefer the bronze screws to the SS ones. Whatever you do, DONT use the epoxy with the steel filler to fill or patch up any low spots etc. #The steel will RUST and you will have awful stains forming on the patch. #The dealer I bought my boat from did this on my boat and it made a real mess, but thats another story.
When you get the tank/s out and you find a hole, you can get it welded up no probs but it must be TIG welded. If the welder knows his stuff, he will use the dry ice method to prep the tank for welding. Definitely insert some inspection holes in the floor and seal the bare timber surfaces with epoxy to maintain the integrity of the plywood. If all this makes good sense to you and you would like more info, dont hesitate to ask.
I know some of this info sounds like a put down of the other guys who have replied. My deepest appologies to all who I have offended. I hope you will understand that I wish only to help Steve out with a better and safer alternative if possible.
:)
Eagle
steveg1100
18-09-2006, 11:03 PM
wow eagle very informative I will take all you wisdom onboard it is much appreciated. I was only going to cut out the side that is leaking at this point but I will probably put an inspection hole on the other side so I can get a visual of what is happening under there if all looks ok will only pull up deck down one side as stated. Looking at the pictures presented by grand marlin an inspection whole will only give you a visual in one of the cavities only.
Pirate_Pete_Tas
19-09-2006, 03:18 PM
Dry Ice is probably the best for the purpose of getting oxygen & vuel vapour out of a tank but if you arnt in a big city with access to Dry Ice then do what most boiler makers I know do use the exhaust.................in the end all you need to do is get rid of the oxygen & while ever the exhaust is pumping in then oxygen cant get in.
steveg1100
24-09-2006, 07:32 PM
Tank is out and small pin hole is found. All welds and seams seem to be perfect found a small pin hole on one side. The tank was insulated on all sides by foam but it appears that was touching a small fiberglass protrusion on the hull side. Took 26 years but a hole was formed. Also not very happy with a slight blemish under the tank. Not leaking but some of the stainless is missing. Following is the images.
steveg1100
24-09-2006, 07:35 PM
Know comes the big question for you learned people should the tank be repaired or will it be weak and a new one has to be made. The rest of the tank is in top condition as mentioned.
steveg1100
24-09-2006, 07:56 PM
When you get around the do I get the tank repaired question then I need to know what is the packing around the tank It appears to be some sought of closed celled foam that must have being poured in around it. You can see some of it still showing on one side of the tank in the previous photo.
Sorry about these questions guys its sometimes easier to get opinion and advice from someone that may have been through it before.
Angla
24-09-2006, 11:43 PM
Is there a chance the packing is space filler. Comes in a pressure can and then expands in the space to fill the void. Can be sawn as it is a foam type of product.
I would probably go a new tank if the cost was not a small portion of the earth.
Chris
steveg1100
25-09-2006, 06:03 PM
Chris
Space filler. Is there a brandname or something so I can do a bit of a search.
Blackened
25-09-2006, 06:13 PM
G'day
If it's the same stuff as i'm thinking, then it can be created by pouring 2 chemicals togeather. It's a space filling closed cell foam. No idea which to chemicals are used but the fibreglass supplies will point you in the right direction. They will have stocks as this stuff is readily used in manufacture of grp.
Dave
Eagle
26-09-2006, 02:54 PM
Hi Steve
Stainless Steel is exactly that!. It "stains less" than ordinary mild steel or the common steel as most people know it. The problem with S.S. is that it will still rust under the correct conditions. from the photos you have shown us, you have the right conditions for the S.S. to rust. Stainless Steel will rust and corrode quickly and badly when the oxygen is removed from the surface of the metal and moisture is still present. The most common sight in this respect are rusted and corroded S.S. bolts that go thru the deck of a boat. The top hex head on the outside of the deck will be bright and shiny. The nut underneath will also be in perfect condition. #BUT, where the shank of the bolt passes thru the deck the oxygen is cut off from the S.S. and the shank will rust away. This is why it is dangerous to bolt deck fittings onto a boat with S.S. bolts and NEVER TAKE THEM OUT for inspection every year. Stainless Steel is "stainless" because an oxide forms on the surface of the metal, it's very thin. and this oxide film is what protects the bolt or surface of the fuel tank. To fully protect the tank from corrosion the surfaces must have free oxygen surounding them all the time. The rust on your tank has formed because there has been water seeping in between the foam and the steel tank. If water can seep in by capillary action between the foam and steel it will displace the air (oxygen) and the surface will rust. Was the rust on the bottom surface of the tank? This would be the most likely area to suffer such damage. I would keep the foam clear of contacting the surface of the tank such that it displaced all the air from contacting the tank itself. If something is constantly rubbing on the surface of the tank, it can rub off the oxide and rust can form vey quickly. Also make sure that no non-stainless steel comes in contact with the tank. Extreme and instant corrosion will result if this happens. You can check this out by leaving an unplated nut or bolt (wet) on the kitchen sink overnight.
Eagle
steveg1100
26-09-2006, 05:25 PM
Eagle
The bottom of the tank has a stain much like the one you see on the side it is a rusty looking smear on one side. The foam has to be in contact with the tank otherwise the tank will move. It is the foam that keeps the tank in position.
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