Replacing rusted out fuel tanks

[rsn48]

A global visual inspection is the only way to really know what problems may exist on the outer surfaces of a tank.

I have talked about my tanks here before, aluminum tanks on a gas boat. Assuming the tanks were originals, the tanks were 50 years old well beyound any stated expected life from an aluminum tank, if you Google. And I have mentioned this before, but I am repeating as even with visual inspection with the tanks removed from the boat, still filled with fuel, there were no apparent leaks until the sun came out and warmed one tank up and a very slight leak appeared. My refit guy wasn't that diligent about removing the fuel and disposing of the tanks from his refit yard until 8 months latter.

When he assigned a guy to drain both tanks and prepare for disposal, both were empty. At no time could we figure out where the tanks leaked from. So visual inspection may not be all its cracked up to be.

 

[JLD]

Do you also see much issues with aluminum water tanks? I understand that chlorine can be very destructive on aluminum tanks if not removed from the incoming water.

Jim

 

[Ken E.]

I'm with the engine removal gang. Not the cheapest alternative, but in addition to having the room to remove the old tanks and install replacements, you'd never have a better time to clean and paint the bilge, clear out old wiring and plumbing and generally renew the engine room. Plus, you'll find a lot of tools that you thought were gone forever.

 

[Datenight]

I Plus, you'll find a lot of tools that you thought were gone forever.

Love it!

Rob

 

[castellah22]

cut the top off the old tank clean it out and put in 3 new tanks inside the old tank ,make a new tank top to replace old one, job done!

 

[FF]

When the new purchasers become savvy enough to demand Monel tanks , all this will be history.

Looks like a wide open market , for a sheet metal shop.

In the day Monel was used for gas, diesel and water.

 

[mvweebles]

When the new purchasers become savvy enough to demand Monel tanks , all this will be history.

Looks like a wide open market , for a sheet metal shop.

In the day Monel was used for gas, diesel and water.

Fiberglass tanks are becoming common in new builds - fiberglass is forever. Most Willard 36s were built with fiberglass tanks. For some reason, mine was not. I suspect it was because my boat was built with stabilizers and the tanks were shortened slightly. I always thought I carried 500 gallons in twin saddle tanks which is the spec on W36 sedans. I frankly have no idea as I the tanks were not calibrated. I replaced each steel tank with twin fiberglass tanks that are about 100g each and lost very little capacity. I'll be very interested to actually see capacity when I fill the tanks in a couple months.

 

[DensPT35]

I'm with the engine removal gang. Not the cheapest alternative, but in addition to having the room to remove the old tanks and install replacements, you'd never have a better time to clean and paint the bilge, clear out old wiring and plumbing and generally renew the engine room. Plus, you'll find a lot of tools that you thought were gone forever.

Exactly what I did. Looked so large when empty. Thought about putting in a pool talbe. LOL

 

[rslifkin]

When the new purchasers become savvy enough to demand Monel tanks , all this will be history.

Looks like a wide open market , for a sheet metal shop.

In the day Monel was used for gas, diesel and water.

Agreed. Monel is really good stuff. The Monel strainer baskets in my sea strainers still look great after 34 years, most of that in salt water.

For tanks, Monel would be good. Fiberglass is also good, but probably only for diesel, as some resins don't do well with Ethanol. Aluminum and stainless can last quite well too, but not quite forever unless conditions are pretty much perfect.

 

[oscar]

cut the top off the old tank clean it out and put in 3 new tanks inside the old tank ,make a new tank top to replace old one, job done!

Except OP can't get to the top as it's right under the deck. So he has to remove the tank either by cutting a hole in the side of the hull, cutting the deck out, or sliding the engine over and bringing it out, probably in pieces, through the inside. That's been the whole point of this thread.

 

[DDW]

Aluminum tanks seem to corrode from the outside in, and usually at the bottom. I had to replace a tank on a sailboat for exactly this reason, and it had to be cut to get it out. If the tanks are placed on sleepers to allow air circulation under them, where the only contact to the boat is not part of the tank wall, this problem disappears. Of course, that costs an extra $30 to build so production builders don't do it. Much cheaper than Monel though. If the tanks are simply placed on something like DriDek, they will do nearly as well. You just don't want several square feet in direct contact with plywood or fiberglass - once wet it never dries.

 

[Ken E.]

When the new purchasers become savvy enough to demand Monel tanks , all this will be history.

Looks like a wide open market , for a sheet metal shop.

In the day Monel was used for gas, diesel and water.

Wasn't Monel also used for hull construction in the past, despite it's high cost?

 

[Barrie]

Hi Bigfish: I could write a book about my adventures with my fuel tank and engine issues. But to summarize i did have one tank replaced by having a hole cut in the hull and dropping in a new tank. The job was perfect. You could never tell there was a hole cut in the fiberglass. I believe my hull is stronger in that spot now because i watched the marina do it and was most impressed. The bad news is that it is an expensive route to go.

I to was told that my bilge pump was pumping fuel into the water, how ever i never saw it myself. Just got the bill from the marina for mopping it up. I was told by a wise person that because my tanks were full, and with the rocking of the boat while tide up, fuel magically can start to flow out the tank overflow. Never saw it; just something to think about.
I had a false bulkheads between the tank and the engine. On the second tank i ripped it out. Gave me a better chance to inspect the tank. So far this tank is holding fine. If i have to replace the 2nd tank i will have it cut up in pieces and removed that way and replace with sectional tanks. I think this would be cheaper.

Bottom line...........no easy solution.

Good luck

Barrie

 

[Miles To Go]

Hello,
Great post about replacing your fuel tanks. I have a 1969 Aft Pilothouse 36 ft., hull 37 and I may have a rust problem on the port fuel tank. We have been hampered here in Demopolis, Alabama with flooding at and around the marina to the point where I have been "trapped" for a couple of weeks on the floating mrina. The hard where Genesis is located has been up to the thighs at one point.

I bought the boat in December but had it surveyed for insurance in January. My surveyor was very thorough and the boat is, generally, in very good shape for a 50 year old boat. I'm not sure the extent yet but the leaks appear to be coming from the rubber hose filler tube. Hopefully.

Just thought I would touch base with you and ask if I could call on you if I have any questions. Any advice you have would be welcome.


Thanks,
Mike Miles
Genesis and Miles To Go
Presently in Demopolis AL

 

[mvweebles]

Hello,
Great post about replacing your fuel tanks. I have a 1969 Aft Pilothouse 36 ft., hull 37 and I may have a rust problem on the port fuel tank.

Mike - are you on Willard Boat Owners group on Groups.IO? There was a recent W36 Motorsailor that replaced one of their tanks. You may find some very specific information

BTW - all are welcome on WBO. We've been around for 20+ years (I am a co-moderator). Traffic has slowed over the years, but we still have 300 members. All are welcome

https://willardboatowners.groups.io

Peter

 

[Grandbanks3642]

Sounds like you're really jammed up and butcher options are on the table. If you're 70 and on a shoestring budget, I'm guessing resale is far down your priority list.

Old tank has to come out. Sawzall and die grinder (after fuel is gone) is your best option, even in small pieces because space is tight. From there, you can probably figure out 25-50 gallon tanks that will allow you to at least move the boat short distances. If longer distances are needed, drums on the aft deck.

This may be a dumb question but if you replace a port 350 gallon tank with smaller tanks (a couple 25-50 gallon tanks) wouldn’t that cause a list to starboard where the other 350 gallon tank is? Not trying to start anything just trying to gain information

Thanks!

 

[rslifkin]

This may be a dumb question but if you replace a port 350 gallon tank with smaller tanks (a couple 25-50 gallon tanks) wouldn’t that cause a list to starboard where the other 350 gallon tank is? Not trying to start anything just trying to gain information

Thanks!

If the new Port setup holds less than 350 gallons and you fill every tank to the top, yes. But if it holds, say, 200 with the new Port tanks, just only fill the Stbd tank to 200 gallons and the listing problem goes away.

 

[Bryant]

Fuel tanks

This may be a dumb question but if you replace a port 350 gallon tank with smaller tanks (a couple 25-50 gallon tanks) wouldn’t that cause a list to starboard where the other 350 gallon tank is? Not trying to start anything just trying to gain information

Thanks!

Yes it would. If one tank needs replacing now, the other one probably does too, or soon will. Do both together. And don’t put 25-50 gal tanks in. You’ll have no range at all and you’ll have to practically give the boat away to sell it. As I stated earlier, My original tanks were replaced with 100 gallon tanks that fit through my main cabin door. Easy to install or replace. That gives me a range of 500-650 miles.

 

[Bryant]

Fuel tanks.

Grand Banks never used cast iron fuel tanks. They used mild steel tanks, sometimes mistakenly called "Black Iron". Also used stainless steel for water tanks, but never cast iron. I apologize if this sounds nit picky, but when we are speaking of different materials used, it helps to be specific, and correct. Glad what you have now is working for you! Safe travels.

You are correct. I meant to type “Black Iron”, which is a pretty commonly used term for them and just mindlessly typed “Cast...”.

 

[Lameka]

President 41 leaking fuel tank

We finally decided that it was time to replace the leaking fuel tank on Lameka. We are now on the hard and after removing 125 gallons of fuel I am in the process of removing the plywood that surrounds the starboard tank. I have been very curious as to how the tanks have been secured in place. From what I can see so far, it appears that they have been secured with a layer of fiberglass that attaches to the hull and comes up about 3” all along the front and each side of the tank. I have not as yet exposed the rear of the tank but I suspect there is fiberglass over the tank there as well. It appears that the bottom and back of the tank are sitting on the hull. Unfortunately it also appears that the tanks sit outboard and below the outer most stringer. That would mean that there is insufficient room above the tank to lift it over the stinger. We could remove the engine to achieve more maneuvering room but I really don’t want to go there. It appears the only option is to cut the tank into smaller pieces. Apparently the whole steel tank weighs about 250 – 300 pounds when empty so cutting the tank into pieces is not unexpected. We will have to be very careful not to cut into the hull in the process!
When I figure out how to attach pictures I hope to give you some idea as to the challenge involved with removing all the wiring attached to the plywood surrounding the tank. I am not looking forward to putting it all back together again.
I will post more pictures as the project continues.
Cheers
Alan McKillop
“Lameka”
1982 President 41 Sundeck

 

[RT Firefly]

Greetings,
Welcome aboard. I'm looking forward to the pictures...Tanks.

 

[Eddie W]

I have to give this thread a thumbs up for a entertainment factor of 10+. Sympathy goes out to OP for his boat and personal issues. Everyone of us will probably be dealing with this issue if we keep a boat long enough, I would guess leaking fuel tanks are the reason many boats are sent off to the boneyard to die.

As for my 2 cents, for any issues that I have, if they are land based or boat based require a diagnostic approach. Currently on this thread we do not know the root cause. Until we know what the root cause is, everything else is just plain conjecture, but entertaining.

 

[slowgoesit]

You are correct. I meant to type “Black Iron”, which is a pretty commonly used term for them and just mindlessly typed “Cast...”.

Bryant, I've NEVER done something like what you described above! . . . well, at least not in the last 10 minutes or so . . . that I can remember . . . What were we talking about?

 

[OldDan1943]

You have my deepest sympathy.
Removing the tank is not the difficult part. Drain it and cut it into pieces.
Putting the new tank in, might be easier to put 2 smaller tanks in place of the one big tank (easier to slide in place) then cross connect the two smaller tanks.

 

[Lepke]

Wasn't Monel also used for hull construction in the past, despite it's high cost?

I've never seen a monel hull, but have always had monel shafts. I have seen copper fuel tanks in navy yard built ship's boats from before WWII.


Iron is used in castings, but never used in sheets since the 1920s (when electric welding became wide spread), especially for tanks because it's difficult to weld and tends to crack. Even riveted ships made after steel became common are made of steel plates. "Black iron" tanks are made of mild steel if they're welded. If they're riveted, maybe iron if they're old. Iron needs to be heated before welding and slowly cooled after. Otherwise it cracks. It wouldn't be competitive to build black iron tanks today, if you could find iron in sheets. Riveting is labor intensive. Ornamental iron work is made of steel except in 3rd world countries.

 

[Lameka]

President 41 leaking fuel tank

I finally figured out how to post pictures. I hope they will give you some idea of what is involved, what has been done and what needs to be done.


Alan

 

[Lou_tribal]

Robert, any update regarding your issue?
Were you able to sort that out?
Please keep us posted!

L

 

[Pete Meisinger]

Funny that your post would reappear after such a long silence. So, bring us up to date on your tribulations..

pete

 

[Lameka]

replacing fuel tanks

After a great deal of time and frustration I finally have both tanks out and have decided on a plan to replace them. My biggest challenge has been designing a platform for the tanks to sit on while allowing adequate space to bolt and screw the flanges into the plywood base and overhead floor joists. As is typical with a boat, nothing is level and nothing is square. The original tank shape changed with the curvature of the hull and I am trying to keep the lines straight in order to minimize costs. I am also trying desperately to avoid removing the engine.

 

[DensPT35]

Fuel Tank Replacement

Sounds like you're only replacing the one tank, I assume you have another tank from the same era. I had to have both done, scaled back the size some which created the need for a platform on both. Had my engine placed up in the salon, supports under for the weight. I have 3 floor panels which a boom truck used to remove the old and bring in the new. Will you be able to put the new tank in place with the engine there? The 4 panels you have does look to give you a great amount of space for work which is nice. I could never have done my project myself. My new tanks came out great and all the new plumbing really cleaned up the entire space. Best of luck! Looking forward to you're finished product shots.