Gas Tank Help

[MYNantucket]

How difficult is it to cut the gas tank out of a boat ? I have a port tank that had a leak when purchased and I fear the starboard tank isn’t far behind. They are both aluminum and in a trapezoid shape 150 gallon. Has anyone done this before ?

 

[rslifkin]

Assuming they're diesel tanks where some cutting can done safely, it shouldn't be too bad. If they're gas, it's a whole different story. But either way, effort to remove depends a lot on the boat in question and where the tanks are mounted.

 

[MYNantucket]

They are gas, tanks are mounted next to both engines on the outer sides below the gunnels. I figure they will have to be cut out of the side of the ship. It could get ugly

 

[Pete Meisinger]

As far as I know you can not cut gas tanks up. I'm no engineer but I have given this problem some thought in the past and I come up empty.

Filling them with water may decrease risk but greatly increase the mess factor. I have thought of filling them with an inert gas but also awfully risky.

There must be a solution but it is beyond me.

The big question is "How does an aluminum gasoline tank develop a leak?" Must be a seam which can be repared if you can find it. There are numerous puttys and caulks which could close an open seam or pinhole.

Keep us posted, this is an interesting thread.

pete

 

[rslifkin]

Personally, with tanks outboard of engines, I'd be more inclined to pull an engine, then a tank rather than cutting the hull. Even a big block gas engine is only about 1000 lbs fully dressed (plus transmission), so figuring out a rig to lift an engine out of the way one at a time shouldn't be too terrible.

And I agree that cutting up the tanks themselves would be a problem. It could be done, but the tanks would have to be drained, force ventilated for a while to get as much residual gas out as possible, and then purged with an inert gas (and kept on a continuous feed while cutting). And I'd still be nervous about it.

 

[Portage_Bay]

Just thinking here. First off this is very high risk. Is the boat worth the risk of your life? Sparks and or heat can explode the unavoidable gas fumes. I'm pretty sure I'd leave it to the pros. Even the pros can screw up, I know of one case where the tech exploded the tank and died in the explosion and fireball.

But if pressed to cut up aluminum tanks.

- Low pressure high volume CO2 to keep the tank full. No oxygen, no explosion. Understand that CO2 is heavier than air and will sink as you open up the tank very possibly rising to the level to suffocate you. You can't smell it or see it. Consider a positive pressure respirator with the air supply well above the working area.

- I'd use a saw. A saw run slowly and lubricated will run cool and not throw off hot bits. Aluminum will gum up the saw teeth making you want to press harder, run faster and thus generate heat. Change blades often.

- Avoid using a grinder. A grinder will get hot and throw off hot bits of abrasive material.

 

[MYNantucket]

The issue with removing the engines is the same. To get the engines out you have to disassemble them and carry out in pieces , I take, heads, then block... Not Fun or cheep. Cutting the tanks up is my best bet. One had been empty for at least three years so it will need to be purged for awhile. I’m not doing the job myself. No Way, it would blow up on me for sure. Thanks for the responses. I have a question in to someone on here that removed theirs but I’m sure they are diesel !

 

[Giggitoni]

It’s a job for Pros. They will most likely clean the tanks first then fill them with a little water and add dry ice as needed to keep the tanks filled with CO2. They will use gas instruments such as a PID (photoionization detector) or LEL (lower explosive limit) meter to make sure they won’t explode when cutting. Tricky stuff. Good luck.

 

[sunchaser]

MYN
How do you know it is a tank leak vs a fitting, hose or bad seal on the fuel level sender? Some years ago I had a strong gas odor on an Al tanked vessel. It was the fill hose and not the tank. The fill hose was only 8 years old and made of the right stuff but the Lake Powell summer heat did it in.

 

[Comodave]

Be very careful of cutting up gas tanks. When I was in the navy the aircraft gas tanks would be purged for about a week just to work on them. In your boat that would be very difficult to do and I still would not be the one putting a cutting tool to the tank. I built a crane and pulled my port engine this winter. I was going to replace one of the fuel tanks but my back gave out so I didn’t get to replace the tank, it isn’t leaking but it is 33 years old. My engine and transmission weigh 1350 pounds. It was easy and took about 2 hours once everything was set up. I just stacked it over the starboard engine on a reinforced deck. Took 3 hours to reinstall the engine. I replaced the transmission damper while the engine was on deck, simple. If you are interested I can send you some photos of the crane I built.

 

[Comodave]

It is possible to cut out the side of the boat to access the tanks. A lot of people will say absolutely not, but it can be done and done correctly it will be fine. There are some adhesives out there now that will be as strong or stronger than the original glass. Get a good fiberglass person to do it. But I would still rather go the engine pull method, I think it will be easier.

 

[alormaria]

Good boat yards can pull an engine and tanks without batting an eye. A lot of gas engined boats have the same problems as diesel ones. And there were a lot more gas engined boats made. The one I dealt with always pulled tanks out whole so they could guarantee the new tank would fit back in.



You need to find a good boat yard that does this on a regular basis.

 

[Solly]

Air hammer and chisel. First part of this video.

When taking cars to the crusher the gas tank had to be open. Used these on steel tanks with residual gas in them. Never liked doing it though.

 

[MYNantucket]

It is possible to cut out the side of the boat to access the tanks. A lot of people will say absolutely not, but it can be done and done correctly it will be fine. There are some adhesives out there now that will be as strong or stronger than the original glass. Get a good fiberglass person to do it. But I would still rather go the engine pull method, I think it will be easier.

Hey Dave, Yes I agree the engine would be simple to pull if I can get a rig setup to do it and support the rig and engine weight... Yes thank you I would like to see your pics of the rig you used and how you supported it... If I could just get the engine up to the salon level I could get the tank out myself... I think lol

 

[MYNantucket]

Be very careful of cutting up gas tanks. When I was in the navy the aircraft gas tanks would be purged for about a week just to work on them. In your boat that would be very difficult to do and I still would not be the one putting a cutting tool to the tank. I built a crane and pulled my port engine this winter. I was going to replace one of the fuel tanks but my back gave out so I didn’t get to replace the tank, it isn’t leaking but it is 33 years old. My engine and transmission weigh 1350 pounds. It was easy and took about 2 hours once everything was set up. I just stacked it over the starboard engine on a reinforced deck. Took 3 hours to reinstall the engine. I replaced the transmission damper while the engine was on deck, simple. If you are interested I can send you some photos of the crane I built.

My email is msdewees@verizon.net, thanks

 

[MYNantucket]

MYN
How do you know it is a tank leak vs a fitting, hose or bad seal on the fuel level sender? Some years ago I had a strong gas odor on an Al tanked vessel. It was the fill hose and not the tank. The fill hose was only 8 years old and made of the right stuff but the Lake Powell summer heat did it in.

I know the tank leaks because I talked to the service guy that has worked on the boat for the past ten years and he gave me the rundown on what he did to combine the two engines to the starboard tank. Thanks for your interest

 

[Comodave]

Hey Dave, Yes I agree the engine would be simple to pull if I can get a rig setup to do it and support the rig and engine weight... Yes thank you I would like to see your pics of the rig you used and how you supported it... If I could just get the engine up to the salon level I could get the tank out myself... I think lol

I just sent you a bunch of photos of my crane setup. If you have any more questions, please feel free to contact me.

 

[rslifkin]

For pulling an engine, you can do what Comodave did and just move it up into the salon, then put it back before doing the other side. No need to get the engine out of the boat, which should mean far less disassembly required.

 

[Pap]

Repair the tanks. Regardless of where it's leaking, it can be repaired. I've repaired more gas tanks than I can recall. Mostly welding but I have used products made for that purpose also. There are even products for coating the inside of the tank, though I doubt useful on a tank that large. Nevertheless, contact a CERTIFIED welder that has experience with tanks. Where ever it's leaking, trust me, it will NOT be new to him or her.

 

[Comodave]

Repair the tanks. Regardless of where it's leaking, it can be repaired. I've repaired more gas tanks than I can recall. Mostly welding but I have used products made for that purpose also. There are even products for coating the inside of the tank, though I doubt useful on a tank that large. Nevertheless, contact a CERTIFIED welder that has experience with tanks. Where ever it's leaking, trust me, it will NOT be new to him or her.

I would never repair a boat fuel tank. If it is old and leaking then replace it. if you fix the current leak who is to say that it won’t start leaking next to the repair tomorrow? Besides the labor getting the tank out and the new one in is the major expense. The cost of the new tank is much less. I wouldn’t want to take the tank out this month, repair it and reinstall it and next month it starts to leak in a different spot. Now you have to pull it out again. No not for me.

 

[rslifkin]

Whether repair makes sense would depend on a through exam of the tank to determine if it's isolated damage or not. And with an aluminum tank, if it's extremally in good shape, coating the inside might be worth it.

 

[MYNantucket]

I just sent you a bunch of photos of my crane setup. If you have any more questions, please feel free to contact me.

Thanks Dave got your pics. So scoring an I-Beam was a major task. You put a lot of work into your apparatus and it worked. That gives me some ideas. I had thought of using thick walled pipes configured in a pyramid inside the salon. I only have about 850 lbs to lift but the key is where you took your support on the stringers. I’m not sure I have the same access. Will have to think about it and take a look at my stringers to see where I can access. I really appreciate you taking the time to send the pics.

 

[MYNantucket]

Oh and I never thought of repairing the tank as it’s aluminum and if pitting in one place it’s probably pitting somewhere else. I think there was a leak around the gas cap that caused the pitting to occur because there is no bonding for the tanks.

 

[psneeld]

Often tanks, especially aluminum may only be corroded in one spot...just depends why.


IF...and only if a pretty decent inspection can be done ....then repair may be a good option.


As Pap suggested, aluminum tank repair on bigger tanks on larger boats, especially commercial ones in my experience aren't new to welders in a marine repair area....call around and check....can't hurt.

 

[C lectric]

Oh and I never thought of repairing the tank as it’s aluminum and if pitting in one place it’s probably pitting somewhere else. I think there was a leak around the gas cap that caused the pitting to occur because there is no bonding for the tanks.

Bonding would NOT stop corrosion from leaks above.

Maintaining a DRY tank outside would have. Deck leaks from whatever source are one of the primary tank wreckers and leaking deck fills are one of the top sources.

 

[koliver]

Thanks Dave got your pics. So scoring an I-Beam was a major task. You put a lot of work into your apparatus and it worked. That gives me some ideas. I had thought of using thick walled pipes configured in a pyramid inside the salon. I only have about 850 lbs to lift but the key is where you took your support on the stringers. I’m not sure I have the same access. Will have to think about it and take a look at my stringers to see where I can access. I really appreciate you taking the time to send the pics.

If you are planning a haulout and will do this repair at that time, consider using a forklift or a truck mounted HIAB crane to lift your engine. Trivial lift for either of those options.

 

[Irish Rambler]

Taking an engine out is no big deal and far better than cutting the boat hull.
Simply remove all excess furniture from the saloon and place sheets/tarpaulins to protect the saloon, remove g/box and alternators etc, no need to take off the heads etc, drain all fluids. Make a frame out of scaffolding and lift the engine with a block and tackle to saloon level and chock it with solid planks below. Then use a forklift with and long lifting bar, attach engine and gently ease it out.
Once the tanks are removed clean the bilges and repaint ready for the engine return.
If they engine's too large to remove then lift the engine to saloon floor level and repair it in situ.

 

[Comodave]

It depends on what configuration the boat is whether or not a forklift can even get into the salon to lift the motor. With my sundeck there is absolutely no access for a forklift to get to the engine. To remove the engine there is a soft patch in the flybridge deck on the port side to take the engine out the top. However the lift has to be very tall to get to it and I would have to remove the hardtop which I won’t do. So I used a beam and moved the engine over to the other side. As to replacing the fuel tank, my back went out right after I pulled the engine. I had 9 procedures on it last year and have about given up on getting it fixed so I decided to not try to replace the fuel tank, mine isn’t leaking but I just wanted to replace it proactively. Instead I just cleaned up the engine room, painted, replaced wiring, replaced hoses, redid the bonding system, etc. i could not have done the work with the engine in place so it worked out ok after all. I took out one transducer and one through hull and glassed them closed. Also was able to replace the head in the aft cabin with a new Marine Elegance since I was able to get to the hoses.

As to repairing a fuel tank, why would you consider that. My new tank was going to be 210 gallons and cost about $2500. If I had the tank replaced by a marina it would cost about $10,000. Why would I spend 3/4 of the cost and still have an old tank that will leak somewhere else at some time in the future and then I pay another $7500 to remove and replace again??? That makes no sense at all, if you pull the tank out then put a new one in. Even if you do the work yourself you don’t want to be doing it a second, or third time. It is a lot of work. Besides a new tank will enhance the value of your boat, or at least make it much more attractive to buyers. Telling the buyers that you repaired a leaking tank would subtract value to me because I would be thinking about the next leak.

 

[Lepke]

I've welded gas tanks using dry ice (makes CO2) and water and fill so just the part you want to weld is out of the water. I don't know if there is a safe way to cut. 50+ years ago, a friend and I were paid to dispose of several old cars long abandoned. When cutting a gas tank, empty for probably decades, the vapor exploded and blew him a good 10 feet in the air. He survived, not much hair on the front. After that we squashed the tanks.

 

[Irish Rambler]

Looking at your Avatar I'm not sure if you have a side door to remove an engine. Failing that lift it with an A frame and then fix it in situ. I've done a couple like that using block & tackle. Your perfectly correct in being cautious with your back, I fell off a roof some time ago so I have to be careful too.
I'm far to particular and certainly wouldn't patch a tank either, get the darn thing out and replace it. I used 316 bright annealed (polished interior) stainless as there's no chance of grunge sticking to it and fitted it with a bottom draw off the same as our trucks, that way any dirt comes right out and gets caught in the filters, after all that's what they're there fore.
When I did mine I took photo's and kept them on file if one day I ever want to sell the boat. I doubt that will happen as we have an ongoing love affair, I know you shouldn't get attached to inanimate objects but boats are different, she's brought me through some heavy waters far above her rating so its payback time with lots of TLC.