# 2000 Cape Horn 24 fuel tank replacement



## FL Aggie (Sep 22, 2013)

Estimates for replacing a 190 gallon aluminum fuel tank were as follows:
$2K for OEM tank, $3K to prep for fiberglass/tank work then finish up, $2.4K to cut floor, remove and replace tank then reinstall deck. So, I'm doing most of it myself.










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## AndyS (Nov 22, 2011)

You can do it! You're an Aggie!

I'm hoping mine never leaks ... but it's 23 years old with the original tank, so ya never know.

_(Keep posting us pictures of the project you go along.)_


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## markw4321 (Oct 4, 2007)

10 years or so I had a Cape Horn 19 with a leaky tank (80 gal). Talked with the cape factory and took it out there.

A couple of their guys did the work as a side job on site for approximately $1200 bucks including the tank.

Times have probably changed but thought I would mention it.


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## FL Aggie (Sep 22, 2013)

Here's the applicable drawings if anyone needs them.










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## JoeyWelch (Sep 25, 2009)

Love a good project.
I've cut a few of them up too.


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## FL Aggie (Sep 22, 2013)

The reason mine is toast is the previous owners allowed the deck plate seals to go beyond their effective service life. In other words, the deck plate seals didn't.


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## JoeyWelch (Sep 25, 2009)

FL Aggie said:


> The reason mine is toast is the previous owners allowed the deck plate seals to go beyond their effective service life. In other words, the deck plate seals didn't.
> 
> 
> Sent from my iPhone using Tapatalk




Are the holes where the capacity tag was on the tank?


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## FL Aggie (Sep 22, 2013)

jlw1972 said:


> Are the holes where the capacity tag was on the tank?




I don't have it out yet so the only holes I know of are right under the deck plate next to the fuel lines and sending unit. 


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## JoeyWelch (Sep 25, 2009)

FL Aggie said:


> I don't have it out yet so the only holes I know of are right under the deck plate next to the fuel lines and sending unit.
> 
> 
> Sent from my iPhone using Tapatalk


Thats where it was on mine.


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## sealark (Sep 27, 2007)

Plastic tanks don't corrode my 89 wellcraft still has it's original plastic tank. Only problem was with the sending unit hold down bolts. easy fix.


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## FL Aggie (Sep 22, 2013)

sealark said:


> Plastic tanks don't corrode my 89 wellcraft still has it's original plastic tank. Only problem was with the sending unit hold down bolts. easy fix.




True, but a plastic tank is still going to cost me more than what I'm paying for an aluminum tank.


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## X-Shark (Oct 3, 2007)

Plastic tanks have no baffels.... It's rare that you can find the correct size that will fit the given hole without losing capacity.

I've always stepped up when it comes to a replacement. I've done a bunch of them.

3/16 instead of 1/8in for anything larger than 60gal.

A custom vent system, so that the tank can vent from either end of the tank.
This cures a slow filling tank problem.
A billet piece for the sending unit.... No machine screws going into a blind hole that has fuel on the other side of that hole.

Tank gets cleaned and sanded, cleaned again, then 2 coats of coal tar epoxy.

Tank gets bolted in, then 4lb density foam. THEN...... The foam gets cut flush with the top of the tank and fiberglass gets laid to cover the foam.... This prevents any water from getting into the foam from a leaking deck plate.

There is also a scupper installed even with the top of the tank, so that if any water has leaked....it will run off and into the bilge.

Better planning makes better performance.


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## sealark (Sep 27, 2007)

I guess I have been lucky getting this much time out of mine. Yes I have had leak problem on the sending unit. Thanks bobby for the other points.


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## X-Shark (Oct 3, 2007)

I did replace a plastic one in a flats skiff with alum.

As you said....Where the sending unit attaches..... Could NOT get it to seal. Tank was warped.


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## Mullethead (Oct 4, 2007)

Please study the advice from X-shark for aluminum tank construction - 

Must be 3/16" for a tank this size - 5083, or 5086 alloy 

Baffles can be 1/8" but most of the time the left overs from the tank skin are available and you apply the same size welds as the tank. 

The billet and no all the way thru screws details are another must for a tank this size. Make sure its pressure tested for leaks -this is large tank with some long welds. 

I have used carbonator gasket sealants on sending units - never even consider silicon or polyurethane 

I avoid Teflon tape (shreds and clogs filters and screens)- and use Teflon paste for screw in fittings. 





X-Shark said:


> Plastic tanks have no baffels.... It's rare that you can find the correct size that will fit the given hole without losing capacity.
> 
> I've always stepped up when it comes to a replacement. I've done a bunch of them.
> 
> ...


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## FL Aggie (Sep 22, 2013)

Mullethead said:


> Please study the advice from X-shark for aluminum tank construction -
> 
> Must be 3/16" for a tank this size - 5083, or 5086 alloy
> 
> ...




Thanks for the input, but I'm not building the tank, just installing it. Cape Horn said "Sheet aluminum. I believe .125 gauge or .150 gauge and the tanks had baffles." 


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## floater1 (Oct 31, 2007)

Call Dennis aluminum in foley no one beats his price for aluminum fuel tank if he usually is about half the price 


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## jasoncooperpcola (Jan 2, 2008)

Does the new fuel tank have to meet epa bullshit or is it grandfathered in?


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## X-Shark (Oct 3, 2007)

jasoncooperpcola said:


> Does the new fuel tank have to meet epa bullshit or is it grandfathered in?



That Gizmo that they are installing in new boats to meet this is going to be a REAL PITA.


I'm sure that will not be involved in this deal.




> Thanks for the input, but I'm not building the tank, just installing it. Cape Horn said "Sheet aluminum. I believe .125 gauge or .150 gauge and the tanks had baffles."


 I see the tank is 17yrs old. Once you do one..... You don't want to do it again.

Pix's for documentation for resale do make a difference.

But with that said.....Putting the same thing in and installed the same way, does not add value. IMO.


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## speckledcroaker (Mar 23, 2012)

Wirelessly posted

Had to put my two cents worth comment in here, why would you stick another aluminum tank in your boat? I have been an aircraft mech since 1978 know a little bout aluminum. Gotta ask what grade aluminum are you using, all weldable aluminums corrode and are prone to cracking at weld joints. The best aluminum that can handle salt environment would be 7075-t6 and it cannot be welded. I would spend a little extra and go with a plastic tank.


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## FL Aggie (Sep 22, 2013)

speckledcroaker said:


> Wirelessly posted
> 
> 
> 
> Had to put my two cents worth comment in here, why would you stick another aluminum tank in your boat? I have been an aircraft mech since 1978 know a little bout aluminum. Gotta ask what grade aluminum are you using, all weldable aluminums corrode and are prone to cracking at weld joints. The best aluminum that can handle salt environment would be 7075-t6 and it cannot be welded. I would spend a little extra and go with a plastic tank.




Unfurtunately there is no foolproof alternative. Poly tanks have their issues too. Bottom line is, after considering all the pros and cons I decided to go back with a custom built version of the OEM tank. This neglected tank lasted 17 years so I don't see why I can't get 20 years with a tank that I take care of. I don't suppose I'll own the boat in 20 years. I really started this post not as a debate since I've already made my decisions, but just to help some people that might have to go down the same road so I hope it helps somebody.


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## X-Shark (Oct 3, 2007)

speckledcroaker said:


> Wirelessly posted
> 
> Had to put my two cents worth comment in here, why would you stick another aluminum tank in your boat? I have been an aircraft mech since 1978 know a little bout aluminum. Gotta ask what grade aluminum are you using, all weldable aluminums corrode and are prone to cracking at weld joints. The best aluminum that can handle salt environment would be 7075-t6 and it cannot be welded. I would spend a little extra and go with a plastic tank.



The alum they use is a 5000 series Marine grade.... 5052 - 5083 - 5086
The 5000 series holds up the best in a marine environment. It is also what they build alum hulls with.

Alum is sort of self healing. IE: When exposed to air it forms a protective coating on it.

The problem comes in with BARE alum and no air. This is what happens when the factories install these tanks , set them in foam for stability and then the deck hatches leak water and that gets into the foam alongside the alum tank.


Plastic tanks: As I said.... Plastic is not the cure all. No baffles, Straps only, They actually permeate fuel smells right thru the plastic.
I've had the flange where the sending unit bolts in that was so warped you could not seal it.


Back to the alum......

So steps must be taken to 

1] Have air circulate all around the alum tank or

2] Seal and protect the alum from the environment.

If you have ever read the articles by Marine Surveyor Dav Pasco. He's dead against foaming a tank in.

http://www.yachtsurvey.com/fueltank.htm

Here's where I shot holes in his way of thinking.

That is fine for a large boat that you can actually get into a engine room and see the tanks. Air can circulate all around it.

But we are talking 17ft to 35ft range boats here.... No air circulates in the bilges of these boats. 

Installing a bare alum tank in these conditions, and your asking for the same results.

4lb density 2 part foam [ not to be confused with spray foam insulation in a can from Homedepot.] :wallbash: Yes I've seen it.


Does a very good job of supporting and securing a fuel tank. But the alum needs to be sealed and protected.... 2 coats of Coal Tar epoxy does a good job of this if the alum is prepped right.

A fuel tank with a few lag bolts or straps does not. If the tank was stagnant it would. But boats get the crap beat out of them.

Remember gas weighs "aprox for figuring purposes" 6 1/2lbs per gal.

So the 190gal tank full of fuel is 1235lbs 

If that comes loose....it's a 1235lb Wrecking Ball with the possibility of a explosion that could REALLY ruin your day.


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## FL Aggie (Sep 22, 2013)

Coal tar epoxy is also part of the plan. 


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## X-Shark (Oct 3, 2007)

Clean the tank with wax & grease remover.......Sand the tank with 80gt on a DA sander. Hand sand where you can't get. Clean the tank again with wax & grease remover.
You get that at a auto body supply store.
Research 2 rag method.

Tape off the areas you don't want the coal tar... Unfortionetly the local Grainger shut down.
https://www.grainger.com/ec/pdf/RUST-OLEUM-Coal-Tar-Epoxy-Technical-Data-Sheet.pdf

You need a 1gal Kit..... That is 1gal of Base and 1qt of Activator.

Don't forget the activator. Only use roller that are designed for EPOXY..... You've been warned.


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## Mullethead (Oct 4, 2007)

At the risk of piling on a bit - 

5000 series is used because of not only corrosion resistance, but 5000 series retains much more strength after welding that other aluminum alloys. 6000 series (6364 is used a lot for tee-tops and the like) looks great, bends into tighter radii that other al alloys, but looses a lot of strength when welded compared to 5000 series. 

7075 is an extremely strong aluminum alloy -
However 
Never use 7000 series aluminum in applications with prolonged exposure to seawater - the high zinc content used to make it strong also make it prone to corrosion - the zinc turns into an anode and goes away! 
Further do not attempt to weld 7000 series- stress cracking the welds (that's why planes are riveted ) 

Good luck and tell us how it turns out


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## FL Aggie (Sep 22, 2013)

So I've been proceeding cautiously, when I have the time to work on it. I finally got the deck off tonight and have started removing the foam so I can get to the tank. I fully expected the deck to come right out after I finished making the cuts but there was foam between the deck and tank keeping the deck from coming out. I tried to using a nail puller and screwdrivers to pry it out, just kept chipping the gel coat without making any progress. I decided I had to get a good point to put a lot of leverage on so I drilled a 2 inch hole. Then I bought some angle iron to lay down under my nail puller so I wouldn't keep chipping the gel coat, that worked great. The combination of the pry bar in the 2" hole and moving the nail puller down the angle iron as it seperated worked great. I kept some small pieces of 1xs in there to hold my progress. The money maker for tonight though was when I decided to put a ratchet strap on the prybar!! Then things really started moving along very nicely!


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## FL Aggie (Sep 22, 2013)

And I'm happy to report that the 2000 Cape Horn 24 has no wood in the floor.


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## OceanDiver (Apr 4, 2016)

I am jealous of the no wood floor. I have a 1999 21 and it still has XL plywood for the floor.


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## FL Aggie (Sep 22, 2013)

Coal tar epoxy time.










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## FL Aggie (Sep 22, 2013)

Coal tar epoxy time










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