Bladder or smaller poly tanks?

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Nopistn

Senior Member
Joined
Feb 18, 2017
Messages
192
Location
USA
Vessel Make
37' C&L Double Cabin
So one of the fuel tanks on my C&L 37 looks like swiss cheese around the fill neck and generally has a lot of rust on the top.
No one seems to think repairing this tank is worthwhile.
I just drained and pulled the inspection port off and in the interior I found 2 baffles and it looked pretty good overall.
This boat has 2 engines and replacing the tank would definitely require removing an engine, if not both and the generator.
I could probably get a few 40ish gallon poly tanks in there maybe with just moving the generator a bit... or I could cut cut the baffles out and put a bladder in.
The current tank is about 150 gallons.
Let me know if yall have any advice or ideas!
 

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I'll try to post pictures of the engine room when I find them or get home and take more... but it's got 2 Ford Lehman's and the generator in a quiet box at the front of the engine room.
 
These pictures are just to give an idea as to how tight the ER is and I was taking them for something unrelated. The fuel tanks are outside of the engines.
 

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Before you go with a bladder determine what effect a bladder will have on your resale price.

If I were in the market for a boat with a bladder I would reduce my offering price by more than the cost of the tank replacement as both a fudge factor and compensation for my hassle.

Replacing a 150 gallon tank with two or three smaller tanks would probably cost less than the potential reduction in the resale price as buyers tend to estimate the costs higher than they would be.
 
Since the tank seems fine below,

It sure looks like there is room to get a wire brush or small grinder to the top of the tank.

I would seal the deck above that is probably the cause of the rust & rot , and simply lay up about 1/4 inch of epoxy and CSM .Lap it over the tank walls about 2 inches to stiffen the tank.

Unless you are in rather extreme conditions the top of the tank is seldom under load , so a good sound repair should be possible.
 
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Bay Pelican said:
Before you go with a bladder determine what effect a bladder will have on your resale price.

If I were in the market for a boat with a bladder I would reduce my offering price by more than the cost of the tank replacement as both a fudge factor and compensation for my hassle.

Replacing a 150 gallon tank with two or three smaller tanks would probably cost less than the potential reduction in the resale price as buyers tend to estimate the costs higher than they would be.
Click to expand...

Sooo you're basically saying poly tanks are much better for resale value.
 
FF said:
Since the tank seems fine below,

It sure looks like there is room to get a wire brush or small grinder to the top of the tank.

I would seal the deck above that is probably the cause of the rust & rot , and simply lay up about 1/4 inch of epoxy and CSM .Lap it over the tank walls about 2 inches to stiffen the tank.

Unless you are in rather extreme conditions the top of the tank is seldom under load , so a good sound repair should be possible.
Click to expand...
Yes the seal around the filler neck is the issue...
The outside of the top of the tank is pretty bad is terms of rust, I'm not sure that would be a long term fix. If yall know someone in the Houston are who might be interested in fixing these tanks or ar least taking a look at them before I cut them out let me know!
 
These are a couple of screen shots from a video I made sticking my cell phone into the inspection port.
 

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Cut the hull side open and take that whole thing out intact, no cutting it up. Get a poly tank of the right size, put it through the open hull side and rest it temporarily on far side of ER. Make good the hull side and then install the new poly tank. Fast, which means time and labor effective. Use a 1st class 'glass guy and you will lose no strength and the hull repair will be invisible. You will get a lift in boat value instead of the mark down that a bladder would bring.
 
Aquabelle said:
Cut the hull side open and take that whole thing out intact, no cutting it up. Get a poly tank of the right size, put it through the open hull side and rest it temporarily on far side of ER. Make good the hull side and then install the new poly tank. Fast, which means time and labor effective. Use a 1st class 'glass guy and you will lose no strength and the hull repair will be invisible. You will get a lift in boat value instead of the mark down that a bladder would bring.
Click to expand...

I briefly thought of that.... but the inside of the hull would be impossible to access to properly glass it back together.
 
I would determine how difficult it would be to remove both engines and the generator. While ir can seem like a huge task, I would think it's only a couple of days to pull them and a little more to reinstall. The main issue is lifting them and removing them from the boat. If that's a reasonable task, I would plan an engine room refit, replacing both tanks with aluminum. IMO, the total cost would likely be about the same as what you will lose on resale if you do a bandaid repair or put in a bladder.

Before going further, I would drain and inspect the other tank.

Ted
 
O C Diver said:
I would determine how difficult it would be to remove both engines and the generator. While ir can seem like a huge task, I would think it's only a couple of days to pull them and a little more to reinstall. The main issue is lifting them and removing them from the boat. If that's a reasonable task, I would plan an engine room refit, replacing both tanks with aluminum. IMO, the total cost would likely be about the same as what you will lose on resale if you do a bandaid repair or put in a bladder.

Before going further, I would drain and inspect the other tank.

Ted
Click to expand...
The other tank holds air but had rust on the top for sure.
 
Nopistn said:
I briefly thought of that.... but the inside of the hull would be impossible to access to properly glass it back together.
Click to expand...
Why? The new poly tank is out of the way, disconnected on other side .of ER on top of other engine. With the old tank gone there's room beside the relevant engine and the hull side to do a proper repair. The new poly tank is installed only after the hull side is reinstated.
 
plus ....


I am pretty sure the glasswork can be done from the outside after the tank is reinstalled...from seeing photos and reading about this procedure.


My guess in this case its easier and cheaper "to pull the engine" route.


One yard that specialized in Grand Banks drops them through the bottom of the boat so the finish work is less and saves a ton of money.
 
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"


"Cut the hull side open and take that whole thing out intact, no cutting it up."

This works great in a well skilled yard with a METAL boat.Steel, or aluminum .

It is death to a GRP boat , although folks have done it.
 
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I have seen vessels with new fill necks welded on a say 1ft square plate and then that plate bolted on the top of tank in place of "swiss cheese" old fill.

Bud
 
...I could probably get a few 40ish gallon poly tanks in there maybe with just moving the generator a bit...

I'm pretty sure you already know this, but to be on the safe side...The poly tanks made to hold water and waste cannot be used to hold fuel because they're made using LINEAR poly that soaks up petroleum products. Fuel tanks must be made from CROSS-LINKED poly and must also be USCG certified that they meet certain standards...no horizontal surface on which liquid can pool, specific types of fittings and fitting locations among others.


Just thought this worth mentioning...


--Peggie
 
psneeld said:
...My guess in this case its easier and cheaper "to pull the engine" route...
Click to expand...

That would be my guess also. When we replaced our tanks we had to pull the engine and running gear. Granted we had a single but it went faster than I thought it would. It took one hour to disconnect the engine and get it ready to pull and 1.5 hours to get it out. It took about 4 hours to reinstall including the hook ups. The only problem is project creep. It’s easy to say, while the engines out lets repaint, replace this or that, etc. You get the idea but you would have great access for the job and when you get done, the boat will be worth more and easier to sell. Good luck with what you decide.
 
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And that's for tank replacements of the same size.

If willing to go smaller tanks, the steel tanks might be cut up in place then the engines just moved slightly to get smaller poly tanks in.

Whole operation lift in, lift out could be done in a day possibly if someone was good at measuring and getting things ready.

Still a lot of work, but much now is diy and by only partly skilled labor.
 
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psneeld said:
And that's for tank replacements of the same size.

If willing to go smaller tanks, the steel tanks might be cut up in place then the engines just moved slightly to get smaller poly tanks in.

Whole operation lift in, lift out could be done in a day possibly if someone was good at measuring and getting things ready.

Still a lot of work, but much now is dry and by only partly skilled labor.
Click to expand...

Yes, smaller poly tanks are what I had in mind while avoiding engines removal.
 
Bud said:
I have seen vessels with new fill necks welded on a say 1ft square plate and then that plate bolted on the top of tank in place of "swiss cheese" old fill.

Bud
Click to expand...


Or gasketed and bolted to avoid welding onboard.
The overall condition of the tanks is too good to warrant removal.
The baffles should have been tall enough to help support the top of the tank, and eliminate the sag that holds water.
I would never build a flat topped tank, even a small slope towards the keel would ensure that it would shed water rather than ponding it.
 
kapnd said:
Or gasketed and bolted to avoid welding onboard.
The overall condition of the tanks is too good to warrant removal.
The baffles should have been tall enough to help support the top of the tank, and eliminate the sag that holds water.
I would never build a flat topped tank, even a small slope towards the keel would ensure that it would shed water rather than ponding it.
Click to expand...

Now that's an idea... I've been afraid of an epoxy/glass patch not permanently adhering due to rust... but a few bolts and some sealant or epoxy might do it!
 
Pretty sure you can’t weld steel once it’s been exposed to diesel oil. My concern would be what does the bottom of the tank look like given water has clearly been getting into the tank for years. A failure would be significant from not only a functional perspective but also an environmental insurance (and USCG fine) perspective.

It’s [beyond] time to replace those tanks.
 
I'd weld in a new top. Or partial top plate. If you kept the tanks full more often, the diesel would protect the tank top from rusting worse than the sides or bottom. My mild steel tanks are 76 years old and look great.
If you seal the top with a new neck and filler, here's some sealants for aircraft tanks that has to work.
A sealed in patch could look poor to a surveyor.


https://www.aircraftspruce.com/menus/ap/fuel_tanksealants.html
 
Let me toss out some ideas.


1) Can the engine be disconnected and temporarily slid back, over, forward to allow the tank(s) to be removed installed? Your hull should be strong enough to block up the engine without doing damage.


2) If the boat isn't used much, and therefore doesn't need a lot of fuel, why not do as you suggest and install some smaller poly tanks. Use one or two as main tanks and the other(s) as long range tanks. Diesel fuel just sitting around can trap condensate and grow bad stuff. Not to mention turning to gel.


3) Diesel is an oil as most know. I wouldn't do any repair work to them or risk cutting them up with something that creates sparks. Also, I doubt any epoxy product will stay bonded to the tanks.


4) Is there a place that a few small tanks can be located? I've seen shelves built in engine rooms specifically to hold fuel tanks. Of course none of the boats I saw this in were used offshore in foul weather. Mostly boats similar to what are found here.
 
ben2go said:
Let me toss out some ideas.


1) Can the engine be disconnected and temporarily slid back, over, forward to allow the tank(s) to be removed installed? Your hull should be strong enough to block up the engine without doing damage.


2) If the boat isn't used much, and therefore doesn't need a lot of fuel, why not do as you suggest and install some smaller poly tanks. Use one or two as main tanks and the other(s) as long range tanks. Diesel fuel just sitting around can trap condensate and grow bad stuff. Not to mention turning to gel.


3) Diesel is an oil as most know. I wouldn't do any repair work to them or risk cutting them up with something that creates sparks. Also, I doubt any epoxy product will stay bonded to the tanks.


4) Is there a place that a few small tanks can be located? I've seen shelves built in engine rooms specifically to hold fuel tanks. Of course none of the boats I saw this in were used offshore in foul weather. Mostly boats similar to what are found here.
Click to expand...

1. Definitely not, I'll post more pics of the engine room if I can find them, otherwise I'll take more when I get back on the 24th.
2. Yes that's kinda my plan. By cutting the steel tanks out I'd probably be able to slide smaller tanks in place.
Alternatively I could fit a pretty big on in the lazarette but it could get in the way for rudder or AC maintenance.
3. I'll cut them up with a sawzall after washing and vacuuming the inside again. And angle grinder might be pushing it though. And I agree with you that I'm not sure anything would bond to something that rusty.
4. See #2. Under the engine room floor I may he able to get another 35 gallons but I'm not so sure it would be smart to put tanks that far below the engine/raycors/ect.
 
Lepke said:
I'd weld in a new top. Or partial top plate. If you kept the tanks full more often, the diesel would protect the tank top from rusting worse than the sides or bottom. My mild steel tanks are 76 years old and look great.
If you seal the top with a new neck and filler, here's some sealants for aircraft tanks that has to work.
A sealed in patch could look poor to a surveyor.


https://www.aircraftspruce.com/menus/ap/fuel_tanksealants.html
Click to expand...

Yes I definitely believe what you said about the rust on the inside after looking inside mine!
But because of limited access to the top of the tank on all sides and the danger of welding on a fuel tank inside of a boat I'm not too sure about this idea.
 
Nopistn said:
But because of limited access to the top of the tank on all sides and the danger of welding on a fuel tank inside of a boat I'm not too sure about this idea.
Click to expand...
My main tanks, about 5'x5'x5', when opened at about 70 years old, had some deep rust pits in the bottom. After draining the fuel, I washed down with a detergent solution. Then welded up the pits. No issues. Used a 12v bilge blower and tubing for fumes. In my youth, I even welded gas tanks.
 
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