Ping Ike, ? bad fuel tank.

[bilgeboy]

Alright, Ike.

You are the fuel tank go-to guy in my opinion. Of course, I invite all the brains at this site to help me out with this problem.

I think I've got a bad one, the aluminum ones I so proudly referred to above.

That section of floor that I showed in another thread came out when I realized a bulkhead I am replacing descended below it. To make a real nice repair of the bulk head, the floor came out.

The real ugly news came with the bulk head all the way out. The ends of the engine stringers are now exposed. The port-most engine stringer is still concealed. His buddy, toward the mid-bilge, is completely dry rotted- wood looked like it was from an extinguished campfire. Starboard side mid-bilge was wet, but doesn't demand immediate attention. The starboard-most stringer is completely saturated with diesel, and the wood can be scooped out of the polyester shell by hand. I thought initially that it was from a previous fuel hose leak that spilled about 5 gallons of fuel in my bilge, since repaired, but the wood keeps oozing diesel. Not even a trickle, but if I dry the area with laquer thinner, come back an hour later, there is a diesel sheen with a small pool, like a milliliter at a rough spot in the hull adjacent to the end of the stringer. I had left a paper bag with some electrical supplies nearby, and the next day the paper was diesel saturated.

The fuel tank sits on a shelf of polyester or gel coated ply, above and separated from the stringer by about 6" of vertical ply. This makes a dead space under the tank to accomodate the curve of the hull. I drilled a couple of holes through the vertical piece so see if diesel is leaking in the space beneath the tank, but my wild-catting came up dry.

There is not even a hint of diesel on the shelf that the tank sits on.

Tank access is not easy, but I can reach around the shelf, and there are no other puddles or hints of diesel on the fuel lines, etc, etc, etc. Given the ugly stringers, I am considering yanking the engine and removing the tank. My dreams are much deeper than my pockets, though, so I wanted to see what your thoughts were on this one.

The guy at the yard recommended making a dipstick from a dowel, and checking the level every week, but I don't think that is a sensitive enough test for such a small leak, if there is a leak at all.

Very interested in your thoughts on that one,

Thanks,

Mike

[Ike]

Oh you definitely have a leak, but from where?? ANy time some one tells me a tank sits on a shelf I immediately suspect that moisture has gotten under the tank and corroded it. But, first have you checked ALL the fittings? Most leaks are from fittings. Some diesel tanks have a drain fitting in the bottom of the tank. It could be loose or the threads could be corroded, or if it's petcock it could be slightly open. Check all the fittings, hoses and lines. I know you dd this by inspection. But the best and surest way to do this is a pressure test. Not usually done with fuel in the tank. Is there any way for you to transfer the fuel out of this tank? There are two types of pressure tests, the soapy solution and the pressure drop test. First you need to find a device that fits into you fuel fill to do this. Many marina's have them. Some surveyors have them. I don't know if they'll let you borrow it or not. Anyway it fits in the fill. if you have a seperate vent line plug it. Surprisingly enough duct tape will do. If you have one of those combo fill and vent fittings the plug should also seal off the vent. then pressurize it to 3 psi. NO More. You can get a soapy solution for this test at most rv or propane suppliers. Many marine suppliers carry it too. DO NOT USE ANYTHING WITH AMMONIA IN IT!Spray the solution on all the connections. If there is a leak it will blow real nice bubbles just like you did with bike tire tubes in water to find leaks when you were a kid.

The other is the pressure drop test and requires a guage. You pump the tank to 3 psi and leave it. If the pressure drops you have a leak. Then you do the soapy solution to find the leak.

Obviously this is a seep, not a major gusher. Either way though it has to be fixed. Your boat isn't going to blow but it will sure make an unholy mess.

I keep thinking it's got to be dripping or draining from some where and the old news paper under the car trick keeps comimg to mind but I don't know if this will work in your situation.

Hopefully some others on this board may have some other ideas as well.

[bilgeboy]

Thanks for the thoughts, Ike. I know typing long responses takes a long time.

I think you are right about the diesel leak. I think I'm going to bite the bullet.....haul out the engine, remove tank and replace. This will give me the opportunity to fix stringers as well. Not looking forward to it, but it will be a learning experience / adventure.

Then just 2 more things,

1- Who makes a good tank in new england, or what should I be looking for ( I know I want a drain down low)

2- Don't go anywhere. I want to set a new tank in place like a pro.

Many thanks,



Mike

[Ike]

DOn't know any builders of tanks in New England. Are you going with aluminum? However I have some contacts maybe you could ask. I have to look them up.

[bilgeboy]

Yeah, I think I'll go back to aluminum.

They are 19 years old. If I kept water out of them and out from under them, I imagine they would have lasted alot longer!

Picked up this tip for a supplier, sounds like a knowledgeable, reputable company. I am not going to low ball a job like that. Too many hacks out there looking for a quick buck in the marine business.

http://lutherswelding.com/

They are in my home state.

Thanks,

Mike

[Ike]

They look good to me. Go for it. Make sure you do a tank pressure test and a system pressure test when everything is installed.

[bilgeboy]

Alright, Ike, I'm going for it!

Seems like a good deal from a reputable company.

$735.00 for a 95 gallon. 0.125" 5052 aluminum.

$90 more for an "exterior coating". Any idea whether this is worth it?

Much abilged,

Mike

[Ike]

I gotta be totally honest with you, I don't know. I have spent years advising people of tanks and fuel systems and yet I have paid no attention to the cost. My focus has been totally on safety. But it sounds like a good deal. May be someone else on this board Like Gonzo, has soem idea of what should cost.

[bilgeboy]

Don't sweat the price, I was actually concerned with what an "exterior coating" was and if it was worth it.

Thanks,

Mike

[Ike]

I sure wouldn't coat an aluminum tank. Why would 5052 need to be painted?