help on a fix Gas tank?

[fatcow]

smelled gasoline in the bilge and had to take a closer look. Seems the gasket around this fixture has seen its days. Pic attached. Looked a little closer and it seems like it has oxides to the point that there might be small holes. i Don't want to remove the fixture to change the gasket as of now so i don't open up a bigger can of worms. My ? is can i just use 5200 for now and play around with it after the season or do u guys have a better suggestion glue wise or a different fix.
thx

[Tfitz]

Gas fumes in the bilge are nothing to "play around" with. Pull it out and replace or take it someplace and have someone fix if possible. Gas tanks are cheap compaired to boat fires/explosions! I forget exactly the numbers but They say one cup gasoline in the bilge is equal to 3 sticks of dynamite! And U know what happens when playing with that. Don't glue it. Count your blessings you caught it early.

[MacCTD]

Just curious, what brand of boat?

[kmorin]

fatcow, I agree with Tftiz, gasoline is safe when its handled correctly and the fuel level sending unit you show is not correct. It does look like there is enough corrosion around the edges to fully discolor the aluminum tank top and the SS flange so I think that's enough to indicate it should be removed and fully repaired.

Those fumes in the bilge should be going up and out the vent hose but seem to have found a easier path to get out of the tank? The risks are not worth taking- 5200 isn't even a 'duct tape' solution from my point of view. The only glues I know about have to be put on bare cleaned metal and the dried before introducing gas form them to work and not dissolve.

Pull the tank, "live long and prosper".

Cheers,
Kevin Morin
Kenai, AK

[gandrfab]

fatcow, I agree with Tftiz, gasoline is safe when its handled correctly and the fuel level sending unit you show is not correct. It does look like there is enough corrosion around the edges to fully discolor the aluminum tank top and the SS flange so I think that's enough to indicate it should be removed and fully repaired.

Those fumes in the bilge should be going up and out the vent hose but seem to have found a easier path to get out of the tank? The risks are not worth taking- 5200 isn't even a 'duct tape' solution from my point of view. The only glues I know about have to be put on bare cleaned metal and the dried before introducing gas form them to work and not dissolve.

Pull the tank, "live long and prosper".

Cheers,
Kevin Morin
Kenai, AK

These guys are correct, most likely not worth repairing.
Poke the corroded spots on the tank with a sharp object most of the time it goes through on old tanks.
Then I tell my customers see not repairable.
Better safe then.......

[fatcow]

will bring it to my tech. This is on my pacific 23fter

[kmorin]

G&R, fatcow, I'm not sure if the tank can be repaired or not... G&R's policy is to dump the tank. I'd repair it in some cases, and I do understand the risks of working on gas tanks, so the evaluation process for me includes the costs of cleaning properly.

If the only area on the entire tank that was corroded was the fuel level sender flange (?) and the tank was in good shape everywhere else, then that small area of welding to repair would mean the rest of the money spent on clean up and prep- added on; was probably still lower cost than a new tank?

I usually plan a few hours at full shop rates to clean a tank, I let the owner do that if they'd like but I still use a steam cleaner or/and pressure washer to clean also. Now days color video bore scopes are so inexpensive (and can be rented in most areas if you don't have access to one) that an inside the tank "look around" is logical before the full cleanup process is done. Why spend all the effort to clean fully if there is extensive interior corrosion and the tank will be junked?

On the other hand, if the tank has so much corrosion that several sites will need to be repaired by cutting out tank wall and replacing it... then the cost of the welding work is a higher cost and combined with the fixed clean up costs that will usually push the project over the cost of a new built tank.

I'm not sure we've heard that the leak is confirmed to be from the sender flange area (?) and looking at the top of the tank is seems to have some organic material there? This implies the bilge is not all that clean and there could be other sites on the tank where problems exist?

I still think I'd pull the tank, even if I lost the entire season, its the 10th season from now I'm hoping to enjoy. Of course, not all shops will accept used tanks for repair, and some jurisdictions may not allow that kind of work, here in rural Alaska tank work is mostly at the call of the shop's policies or preferences. I do tank repair in some cases, but bill accordingly.

Cheers,
Kevin Morin
Kenai, AK

[MacCTD]

Has anyone replaced a tank in a Pacfic? I would think it would be a pretty involved process, having to cut out the floor and then the tank. I wonder if the tank failed in that area from water leaking from the Armstrong hatch cover?

[welder]

Don't know of anyone that has had to pull an Alloy tank yet but yes the deck will be cut to pull the tank, not a real big deal just time. That's the cool part of alloy boats, cut it off-weld it back on.
FYI, the 115 gallon tank is about Nine Feet long. Julie can tell you the exact dimensions so you know where to cut for a clean repair if needed.

[capesteve]

Wow, replacing a tank sounds like a huge deal to me!! Do you need to cut a 9 foot hole in the deck? If so does that mean removing the seat and center console to get to the deck? Sounds very expensive.

I am interested in any insights as to how and why this happened. Salt water getting in through the hatch cover has been suggested, any evidence of that? Has any other Pacific owner had this problem? Ill have to take a closer look at mine.

Last question: I can only see a small part of the tank through through the deck hatch, and have never inspected the other parts of the tank, but assume it is ok. Is there any easy way to do a thorough inspection?

[kmorin]

Pacific Owners with below decks tanks,

I'm not intimate with the boats so these remarks are generic more than any 'last word' and the surely don't represent Pacific. But I've built a few boats, and done repair on more so I'll just get some items listed here for general knowledge from experience.

As to tank install, if they are below a sealed deck the deck will have to be cut out.... but that is only an hour's work. A skill saw set to the deck thickness (they can be adjust very exactly for depth of cut) run along lines laid out on the deck will cut out the deck panel in question in an hour's work. The keyholes or 'field welds' onto other framing will take longer to locate and remove IF they exist? That is; some decks will require removal of the field welds while other will not?

If the framing of panel over the tank were designed to be removed? (have to ask Pacific) then... the framing could be stubbed to the sides of that panel so the deck cut was all that is required to make in order to remove a central panel. I've used this type of deck framing before and it works well in tank removal, so consult the Pacific build pics to see?

Next is the question about what might cause corrosion of a below decks tank? The main question is the presence or absence of bilge humidity and or water. Even a deck without any access or inspection hatches should be vented with a 'breather tube' to allow air to expand and escape and to contract and flow into the below decks spaces. All deck hatch fittings, depending on the presence of the breather tube fittings above, would be possibly subject to vacuum in the later part of any given day when the ambient air cools.

IF the deck spaces are not vented or inadequately vented (someone put a cap on the vent tube!) then as the sun went down on a warm metal boat it would cool, contracting the volume of air under the deck forming a vacuum under the deck. When the vacuum formed the outside air will 'push in' through the deck hatch's seals to allow the air pressure to equalize.

If the hatch has been wetted during the day, (and) if that hatch's recesses were full of fish gurrey (sp?) or other organic material.... then that material will be forced into the bilge and if the tank or tank fitting is immediately below???? well the bilge is going to get a compost contribution! Another contribution may be salt water which is more conductive than rain water, so the potential for a corrosion cell forming is higher than fresh water boats but both sources of electrolyte will work just fine in contributing to corrosion cells.

Why do I know this fact? I in 1979 I built a 40'x16'x4 welded aluminum fish scow (not powered) and used 2" pipe vents into the 'box' and two deck hatch called Freeman Oval Hatches that welded into the deck and were water tight, to allow work and inspection inside these big hollow metal boxes. However, some cannery employee didn't understand the purpose of the port and starboard 2" pipe risers with goosenecks and threaded fittings - so they plugged them with plastic pipe thread plugs to be 'safe'.

I was called to the cannery several years later to inspect a "mysterious ring of corrosion" inside the scow(s). Immediately below each Freeman Oval was an oval shaped 1" wide track of corrosion in the 1/4" bottom of the scow! I went to the vent stanchions and found the plugs, my first reaction was that the hatches had been sucking in during the vacuum portion of the day's temp swings. The rubber seals on the hatches were working as vacuum relief valves! Not good.

I washed the bilges with 5gal. of ammonia & water and neutralized the acid cell corrosion sites, then drained the hull and made sure the owners understood the vents kept the pressure equalized and the Freeman's held out the water and fish slime mixture after that.

So this can happen if the bilge of a sealed deck is not vented. I'm not sure if this is contributing to the problem being discussed? but its worth a look at the boat in question to see. One thing that seems obvious to me from the photo posted is the tank top is not clean like I'd have expected in a bilge that was not getting some "unwanted fluids down the hatch?" Not sure where the brown contaminant came from but it looks like the hatch above may not be sealed?

How to inspect a sealed deck boat? Well the most cost effective is the video bore scope. even with an extension the cost of these is not very high compared to the cost of allowing uncontrolled corrosion to work freely in a bilge that is starved of oxygen- the healing chemical for all marine aluminum alloys. These tools may be rented too so if you don't want to buy they may still be available?

What if you do find bilge contamination and corrosion? First and foremost is to be able to define your boats' construction. IF you do have a hull drain, and you do have a forward bilge hatch or deck fitting allowing access to the bilge (?) then you could plan to tilt the boat up, bow high, and rinse it the dry it out.

Depending on the pretense of foam, limber holes (some call these mouse holes) and other flow restrictions of bilge drainage rinsing can be a hard job to accomplish. Depending on the amount of bilge water or dryness of the bilge (under deck area) the rinse may be fresh water or a base solution of baking soda or ammonia water to neutralize any acidic residues in the bilge. But once water is introduced into the bilges , drying out is important too.

Last, drying the bilges after rinsing is a very big deal- super critically important step in this maintenance process, and can be done by just venting the bilge if you live where its warm and a few sunny days on the trailer allow the boat to get 'hot' inside?

OK, long post but I have to drag out the soap box now. Mill scale left on aluminum inside the sealed deck, including the outsides surfaces of tanks, and super especially tanks that are not domed top, sloped tops, or other wise allowed to dry off.... promotes a galvanic corrosion cell. This is not agreed by all builders, most don't strip mill scale from their bilges and will say I'm off the mark saying this is important. But, I've opened up many name brand builders' boats only to find the inside of the boat had much greater corrosion than the outsides, and the reason is the fact I've stated above.

I've even been involved in a very heated exchange with a major PNW builder's customer service dept (welding guarantee issues) more or less brought in by the local Alaskan owner of the Puget Sound (region) built boat - as a 3rd party witness. The builder told the owner the photographic evidence of the bilge corrosion in the bore scope pictures were " a natural occurrence to all aluminum boats" (!) That is not true, it may be in their boats, and that might be true of others' (?) but if the mill scale is removed during construction and prior to sealing the deck, GALVANIC corrosion does not form- crevice or poultice corrosion - maybe but not galvanic (dissimilar metals caused).

Hope to have provided a few reference points of discussion, as always, it is only reasonable to mention that I am the AAB.com's resident, self-described, Mill Scale gnat-zee and harp on this topic continually. My views are not accepted too widely in the current welded building industry; but I've repaired/modified/rebuilt boats as old as cannery boats built in the later 50's and early 60's so my perspective remains based on that level of experience- not just a 10 or 20 year stint building- recently.

I choose to rely on my 65 years of boat history exposure to shorter historic perspectives regarding mill scale's long term impact on our boats.

Cheers,
Kevin Morin
Kenai, AK

[gandrfab]

G&R, fatcow, Has never seen a tank with just one small corrosion spot, just about all the tanks I have replace were foamed in.
G&R recommends against foam, but doesn't mind the work he gets from it.

[kmorin]

G&R, I agree that foamed in - unpainted tanks not prepared for paint- is about as good a guarantee of work for a shop as the builders could provide!

This is another example of good designers and builders either being ill-informed about the combined results OR they just don't care if they can get the boat out their door? Foam in the bilge is a lot like mill scale or no vents, just not a good idea; in fact I'd say unless it was installed right (?) its poor building practice.

Cheers,
Kevin Morin
Kenai, AK

[capesteve]

Fatcow any updates on your tank? I am curious what was found....

[fatcow]

Sorry for the late update. After having the tank checked out by a couple of people it was found that the tank was solid except for the spot where the sending unit stainless, was put onto the aluminum tank. It had pitted around the sending unit. Instead of going with a all out remove the tank fix i opted to do a quick not permanent repair. I believe they used a two part epoxy. It came out great how long will it last is anyones guess. Will try to get pics up in the next couple of days

[Katoh]

A big problem when using dissimilar metal metals together I.E stainless bolts on Aluminium tank is the galvanic corrosion that occurs when the more noble metal sacrifices the weaker to preserve itself, in your case the stainless bolt ate the aluminium tank where it was in contact with it. A good workaround for this is to isolate both metals from each other using products like Duralac on the threads and a poly washer. I am pretty certain there are offer products on the market but that’s the one that I use here.
Prevention goes a long way in not having troubles later.