Fuel tank dilemma, help please

ulysses said:

...we hardly ever blew one up.

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IN a steel vessel , chopping a hole makes sense ,in GRP to me its insanity.Criminal.

I would have the tanks chopped out piece by piece , and install as many plastic tanks as required., with one real metal fuel tank per side.

The big advantage (besides cost and structural problems) is the tanks can be only filled as required.

Sitting with huge tanks watching bugs grow or ashphalting is not fun.

By installing a marine furl tank on either side ,(if there is room) and having boxes of fuel to refill the tank underway you have an ideal cruising setup.

As good as a day tank, but easier to service.

The only fuel aboard would be in the marine tank , where water can easily be removed , and the fuel boxes would be filled before any long trip.

There are many differences between a marine fuel tank and a box of fuel , that have been covered many times, in the archives.

Faced with this choice we did not cut the hull. Replaced each 300 gallon tank with two 110 gallon tanks. Love the ability to control the fuel storage with four tanks.

As to the second tank in your case, our story is a good lesson. Starboard tank leaked. Decided to replace both tanks without seeing a leak on port side. After replacing starboard tank went to remove the plywood covering the port tank and the port tank split along a rust seam releasing the three inches of water we had used in flushing the tank of diesel. Glad that didn't happen underway with a couple of hundred gallons of diesel.

Bay Pelican said:

Faced with this choice we did not cut the hull. Replaced each 300 gallon tank with two 110 gallon tanks. Love the ability to control the fuel storage with four tanks.

As to the second tank in your case, our story is a good lesson. Starboard tank leaked. Decided to replace both tanks without seeing a leak on port side. After replacing starboard tank went to remove the plywood covering the port tank and the port tank split along a rust seam releasing the three inches of water we had used in flushing the tank of diesel. Glad that didn't happen underway with a couple of hundred gallons of diesel.

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The PO of our KK42 cut out the black iron tanks with a saws all and replaced with one 200 and one 180 gal on each side. Replacement material was aluminum. The engine room is as dry as a bone and I doubt that there would be a corrosion issue anytime soon on the tanks. The PO also put in a fuel polishing system. Once the fuel levels are low enough, I move fuel from tank to tank to "polish" all remaining fuel at least once a year. I also keep track of the age of fuel, ensuring the older fuel is in the forward tanks from which the engine draws fuel.


Racor 900's and a fuel polishing system.



Jim
Sent from my iPad using Trawler Forum

FF said:

IN a steel vessel , chopping a hole makes sense ,in GRP to me its insanity.Criminal.

I would have the tanks chopped out piece by piece , and install as many plastic tanks as required., with one real metal fuel tank per side.

The big advantage (besides cost and structural problems) is the tanks can be only filled as required.

Sitting with huge tanks watching bugs grow or ashphalting is not fun.

By installing a marine furl tank on either side ,(if there is room) and having boxes of fuel to refill the tank underway you have an ideal cruising setup.

As good as a day tank, but easier to service.

The only fuel aboard would be in the marine tank , where water can easily be removed , and the fuel boxes would be filled before any long trip.

There are many differences between a marine fuel tank and a box of fuel , that have been covered many times, in the archives.

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Trying to digest all of these great recs over night, I first looked realistically at the types of cruising I'll be doing. 99.99% of the time it will be day cruising from marina to marina with a few anchorages every now and then along the Gulf coast from N.O. to Destin areas. Maybe a crossing to Tarpon Springs down the road. Fuel burn would be 100 gallons a day at most. FF makes a huge point in all that fuel sitting in tanks going downhill in quality. I would much prefer to use fresh fuel on each trip then keeping fuel in tanks for months at a time. Multiple smaller tanks with a 75 gallon main fuel tank on each side makes great sense. Would be hard to burn that much fuel even in 2 days cruising at 8 knots. I do not run those cats at WOT. Keeping a few smaller transfer tanks would not be used hardly at all. Making a smaller main tank should make it easier to install without tearing up my boat or engines. Granted the access to the old tanks is very tight however both ends of the tanks are clearly exposed. Just need a small young person to get in there and cut away!

Thinking about space in the engine room the aft section behind the trannies has a shelf all across the beam of the boat. On it are the 2 starting batteries which can easily be moved to their original spot in front of the engines. There is the hot water heater in the center. This can easily be moved to either side leaving me with over 9ft x 2ft of shelf space with 3 ft of height. I could condemn both saddle tanks, build 2 90 gallon tanks set on that shelf. Gives me 160 gallons of usable fuel. I do have an aluminum 100 gallon reserve tank forward of the engine room set beneath the galley center line. Has a transfer pump and fill on deck. This hooks to the port tank with an equalizing fuel line between the saddle tanks. I've never used this tank because I've never needed to burn 400 gallons of fuel. Seems thi can give me even more options.

Thanks for all of these helpful replies. Probably use recs from a bunch of these posts!

I really, really don't want to cut the sides of my boat.......

I have read several posts on first page of this thread but not all in the thread... so what I mention may have been already stated.

Seems you know that leak is approximately mid high on hull side of tank... odd location to say the least! I'd first get both tanks fully inspected to learn general condition. If the condition showed replacement was in order you unfortunately have expensive and time consuming choices to make.

But - if not too bad a prognosis, i.e. that the tanks in general should have years of usefulness remaining... I would guess that a seam badly welded from factory let loose or that something in that location had for years been hitting or rusting the tank and it ruptured. In that case I would determine exactly where the rupture is and would think seriously of cutting small hole in hull side for repair. Hole may not need to be more than a few inches to a foot round or square. FRP repair would be minimal and hull integrity would remain the same.

You should be able to get a visual on the tank's actual offending location onto computer screen via flexible extender arm cameras.

Best luck!

I had a friend that had his tanks lined with something, his description sounded a lot like what is in this thread.
http://www.trawlerforum.com/forums/s6/diesel-fuel-tank-repair-internal-coating-3719.html

ragin cajun said:

I really, really don't want to cut the sides of my boat.......

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I agree, last resort imo, exhaust every other financially and physically reasonable possibility before you do that.

JDCAVE said:

The PO of our KK42 cut out the black iron tanks with a saws all and replaced with one 200 and one 180 gal on each side. Replacement material was aluminum. The engine room is as dry as a bone and I doubt that there would be a corrosion issue anytime soon on the tanks. The PO also put in a fuel polishing system. Once the fuel levels are low enough, I move fuel from tank to tank to "polish" all remaining fuel at least once a year. I also keep track of the age of fuel, ensuring the older fuel is in the forward tanks from which the engine draws fuel.
View attachment 40591

Racor 900's and a fuel polishing system.
View attachment 40592


Jim
Sent from my iPad using Trawler Forum

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That's a really nice, clean, well organized ER. Congrats.

X2. J D Cave.

That is Beautiful, if that were mine I would want to work a long time down there just enjoying the surroundings and listening to great music.

Regards.

David.

Thanks, but I can not take credit. It was all the PO's hard work. It was one of the compelling reasons we bought this particular boat.


Jim
Sent from my iPad using Trawler Forum

Cajun...
I like the way you think, and I do agree that boat cutting suxs. With the forward tank available, you seem to think it is clean, seems to me if you engineer the plumbing correctly you can have the best fuel system ever. That dry ice deal is great, just make sure YOU are ventilated too.

Should you choose aluminum (my choice) remember it is a very sacrificial metal. Even countersunk steel screws the humidity in the air will set up electrolysis. The bunks they set on should be covered with light cloth and glassed, same with the new tanks. This is cheap and easy. Be very, very sure no superior metal can touch. I used the above techniques and removed all retaining straps and glued them down with 5200. Could glassem in I guess. Under tank ventilation might be good too, anything to keep moisture away. And bonded the tanks, of course.

Each baffle (may not need baffles with multiple small tanks) should have access plates, or at the minimum 2- 3/8" or larger access holes for a fuel polisher to shove tubes into to churn, filter and recirculate your fuel.

Lastly, insofar as most Diesel engine failures are caused by bad fuel either existing trash in tank(s) or a bad load. Cases like this negates most of the advantage of twins, one gets skunk fuel both get skunk fuel, both go down. Why not have a day tank where you filter the next days fuel each evening, easily checking vacuum, filters and water content BEFORE getting underway? Then you KNOW you are good to go. With the process you are about to go through accomplishing should all be a small additional dollar add on(s).

Our boat has 4 new aluminum tanks . 2 @ 125gal and 2 @ 55 gal . I'm not sure what the original tanks were, but it played a big part in our decision to purchase this boat . The install is good but I wish they would have done a neater job getting the old ones out , but slicking the area up is on my long list of things to do .

Pack Mule said:

Our boat has 4 new aluminum tanks . 2 @ 125gal and 2 @ 55 gal . I'm not sure what the original tanks were, but it played a big part in our decision to purchase this boat . The install is good but I wish they would have done a neater job getting the old ones out , but slicking the area up is on my long list of things to do .

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Hi Marty - At 360 total gals (288 w/ 20% reserve) what is your longest cruising range at most economical speed?

Had tank issues on the Jefferson. Pulled both tanks by hanging engines over each other while putting in tanks. Of course I have Perkins so not as big as your engines. Yard weaned to cut hull also but I questioned how they were to glass ribs behind engines,they had no answer. Did it myself with help from guys I gave fuel to. Good luck.

If you can get any access to the side of the tank, I would look into cutting a hole in the side large enough to work with and then possibly drop a flexible rubber type bladder in there....have you looked at that option?
Much cheaper than the other methods and may work well.

Taras said:

If you can get any access to the side of the tank, I would look into cutting a hole in the side large enough to work with and then possibly drop a flexible rubber type bladder in there....have you looked at that option?
Much cheaper than the other methods and may work well.

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How would you get the tank baffles out?

"How would you get the tank baffles out?"

A cut off wheel and perhaps drilling any rivets .

Ragin Cajun, my boat had exactly this same issue with leaking main tanks. The PO avoided radical surgery by leaving the tanks in there sealed off empty, (I think of them as buoyancy tanks now), and he grabbed the stainless steel tanks in the lazaret for the fuel. The original tanks would have been about 1200L each - way more than ever needed, these stainless tanks are 800L each, and have always been more than we ever needed. I have never even completely filled them.

I the PO made do with a large bladder for water, but I have fitted food grade plastic water tanks inboard of the fuel tanks, also in the lazaret and so they are all easily accessible. The trim is better than before and down wind/sea handling also better. Time has proven this solution was fine, 15 ys later.

However, in your situation, I think FF's suggestion of having the tanks (both of them) cut out enough to fit fuel grade plastic tanks in there, (why bother with any corrodible metal in this day and age?), even if less in volume, especially as they may foist ethanol type mixed fuels which are not great for aluminium on you later on. Also, as FF suggested, best as say 4 tanks, (2 each side), set up so 2 could be kept as reserve tanks for the odd long distance run, but 2 are probably plenty for virtually all other running. You are not going to cross oceans.

If you have them drain from the bottom via connections with taps, you can control what goes where, and if they finally run through easily spun off and changed filters, you can forget the need for fuel polishing, as it is automatic with this system - no crud can form if always draining from the bottom, (Nordhavns do this), and mine is set up like that. My filters last years. If you have the tanks linked side to side they auto-level, and you can even just fill from one side if taken slowly.

The idea of moving perfectly good engines or hacking the sides out is the last resort in my view also, as others have said. and doing just one side is likely to be only a temporary fix, so then you'd have to do the same to the other side anyway.

The above based on personal experience. If I wanted to ever do really long distances in my boat, I'd have the old iron tanks modified by just cutting out the side and the baffles, and the aft end for ease of sliding in the new (smaller = easier to fit) plastic tanks, leaving a sort of trough of steel as a base on each side, (the back side and top could probably be left there for strength and to secure the plastic tanks to, and have fuel grade plastic tanks sat in them and linked via taps to the existing tank fuel lines. I think bladders, as Taras suggested, might not be ideal for fuel in case of the odd sharp edge and some movement not being a good combination.

Just a few thoughts to ponder. Not sure why so few mentioned plastic/synthetic tanks as an option. These are not attacked by corrosion, or dissolved by alcohol as long as the correct type.

yachtbrokerguy said:

I suggest you find a good marine surveyor to look at the boat, look at both tanks, look at moving the engine(s). At the boat yard where I work the yard management really likes a qualified outside surveyor to advise the owner and then there is never a question of the yard suggesting too much work at a higher cost. Plus the documentation from the surveyor will help when selling the boat sometime in the future, and might help in an increase in value, although the increase will be less than your expense.
Here is a picture of an aluminum yacht getting new engines but aluminum is easier to cut and weld back at full strength.

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Great idea - and great picture too!


1983 Present 42 Sundeck
Twin Lehman 135's

Peter B said:

Not sure why so few mentioned plastic/synthetic tanks as an option. These are not attacked by corrosion, or dissolved by alcohol as long as the correct type.

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Baffles, required for larger tanks, are hard to attach to plastic.

I have fiberglass tanks, built in place. I expect no failures in my lifetime, and condensation inside the tanks is minimal.

Interesting link on refitting old steel tanks with bladders.
Retro-Fit Your Failed OEM Rigid Fuel Tank With A Flexible ATL Fuel Bladder!

Compared to all other alternatives, this just has to be the way to go for those who have to nearly destroy the boat to remove the old tanks. Like me for instance! Mine are fiberglass encased steel and while they haven't failed yet I have an almost imperceptible leak from somewhere so I know it is virtually inevitable. The welded fittings are rusting so who knows what shape the thin steel is in under the glass. I have 4 200 gal main tanks and two 100 gal keel / day tanks for a total of 1000 gal. I live in terror of the call from the marina that a tank has failed and my bilge pumps just pumped hundreds of gallons of fuel into the water of the marina. I doubt any amount of insurance would cover the plethora of environmental and civil lawsuits that would surely follow.

Not sure if these bladders would work in many instances though as it appears that they must be inserted & assembled through the top. In my case, as in many, the tank top is only 2 inches from the salon floor.

I think Pete has a great idea of inserting plastic tanks in the old tanks but again, if you have the room to do that much cutting, I wonder if it wouldn't be prudent to just keep going. That said, I fully agree that properly constructed plastic replacement tanks just have to be the way to go.

If it were my boat I'd just let them cut the old tanks out and put in new ones.

I understand not wanting boat surgery but fiberglass is pretty easy to work with in the right hands.

Heck, I've seen several boats over the years that were literally cut in half and a hull extension glassed in. If they can do that kind of work safely they can fix the holes for your tanks.

ksanders said:

If it were my boat I'd just let them cut the old tanks out and put in new ones.

I understand not wanting boat surgery but fiberglass is pretty easy to work with in the right hands.

Heck, I've seen several boats over the years that were literally cut in half and a hull extension glassed in. If they can do that kind of work safely they can fix the holes for your tanks.

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After 2 days going over every possible scenario with boat yard, the cramped engine room left little choice in my decision towards those fuel tanks. The option of removing those 3208s, pulling the trans, turbos and risers then building an A frame hoist system to raise engines would have required taking out front windows then the side salon windows also. This would have torn up my newly finished salon and galley. I was shown 3 boats where the sides were removed to get to fuel tanks then reglassed both inside and out. I would say the repair was better/stronger than the original sides. No way to tell where cuts were made along with a new paint job to boot.

There was no access to the tanks with engines in place to cut out even the sides of those tanks to repair or place bladders inside. Repair cost would have been almost the same to pull engines if nothing needed to be replaced or repaired on them which we all know something will break doing that kind of work.

I went with side removal of tanks. I feel better knowing first hand the quality of fiberglass work that these guys do. I'll get a boat that her fuel system will be all new. No more worrying about a bilge dumping fuel all over Lake Pontchartrain. I have had nightmares over this...not any more.

To all potential boat/trawler buyers, please look closely at any boat with fiberglassed in iron fuel tanks! Be sure you have access to them without having to go through the tear down some of us have gone through.

ragin cajun

Please post pics of the project as it happens so we can learn something. My biggist worry about the process is how can they glass the inside of the hull. Maybe (probably) they know some tricks that I do not.

FF said:

"How would you get the tank baffles out?"

A cut off wheel and perhaps drilling any rivets .

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My point was, how are you going to reach them through the small hole that most tanks have as access? And if you could reach all the mounting points you'd have to be even more of a contortionist to reach in and cut them up into small enough pieces to fit through the hole.

ragin cajun said:

After 2 days going over every possible scenario with boat yard, the cramped engine room left little choice in my decision towards those fuel tanks. The option of removing those 3208s, pulling the trans, turbos and risers then building an A frame hoist system to raise engines would have required taking out front windows then the side salon windows also. This would have torn up my newly finished salon and galley. I was shown 3 boats where the sides were removed to get to fuel tanks then reglassed both inside and out. I would say the repair was better/stronger than the original sides. No way to tell where cuts were made along with a new paint job to boot.

There was no access to the tanks with engines in place to cut out even the sides of those tanks to repair or place bladders inside. Repair cost would have been almost the same to pull engines if nothing needed to be replaced or repaired on them which we all know something will break doing that kind of work.

I went with side removal of tanks. I feel better knowing first hand the quality of fiberglass work that these guys do. I'll get a boat that her fuel system will be all new. No more worrying about a bilge dumping fuel all over Lake Pontchartrain. I have had nightmares over this...not any more.

To all potential boat/trawler buyers, please look closely at any boat with fiberglassed in iron fuel tanks! Be sure you have access to them without having to go through the tear down some of us have gone through.

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Good for you. You made the right decision IMO.

Ragin Cajun- I would love to see pictures as you progress.


1983 Present 42 Sundeck
Twin Lehman 135's

ragin cajun said:

There was no access to the tanks with engines in place to cut out even the sides of those tanks to repair or place bladders inside. Repair cost would have been almost the same to pull engines if nothing needed to be replaced or repaired on them which we all know something will break doing that kind of work.

I went with side removal of tanks. I feel better knowing first hand the quality of fiberglass work that these guys do. I'll get a boat that her fuel system will be all new. No more worrying about a bilge dumping fuel all over Lake Pontchartrain. I have had nightmares over this...not any more.

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Fair enough, but still worth considering fuel grade plastic tanks as the replacements, I would think..? They would be a cinch to install if you're cutting open the hull, can be shaped to match the side of the hull, so take up less width = ER space round engines better, and they'll never corrode, or be eaten away by synthetic/alternative fuels if these become mandated in the future. Just a thought.

Oxford Yacht Agency in MD has replaced many fuel tanks on GBs. They routinely cut the hull bottom and drop the tanks out. Wouldn't worry me in the least if I had faith in the yard and they had done the job before.