18 Fuel Tank question

[Beaver]

I'm finally getting around to pulling my fuel tank but have a couple questions...

1) I have drained all the fuel but have read where guys recommend adding soap and water to the tank and draining prior to pulling and disposal. Is this an important step?

2) Any suggestions on disposal of the old tank?

3) I read that I should attach neoprene to the bottom to help it from sliding around. It s a Moeller poly tank, should I do this?

There is probably a bunch of questions I don't even know to ask so any feedback is greatly appreciated.

Thanks.

Rob

[FLexpat]

I sold my old one for scrap aluminum - I think I got 15 or 20 bucks. Most of the residual gas had evaporated from sitting in the sun so I didn't worry about it.

[rcnight]

Recently replaced my 70 gallon tank. Drain before removing. I did rinse the inside with a soapy solution but not sure you need to if you let thoroughly dry. There's an article with instructions by a marine surveyor about installation I followed - do a search and I'm sure you'll find many. Get rid of all the foam and provide air circulation to prevent corrosion. The outside of my tank was heavily corroded, inside was pristine except for the two holes. Most important, coat your tank if going with aluminum. Coal tar epoxy seems to be a favorite. I used my circular saw and cut it in half - very loud. Most scrap yards will pay you more if properly sized. Good luck.

[erebus]

You can use neoprene, or pretty much whatever you have on hand if its a poly tank.
Neoprene is standard with aluminum tanks, because the neoprene will not react with the aluminum if any salt water sneaks into the tank area.
Because you're using poly you can use pretty much anything.
I installed my poly tank in my 18 with some cleats I made out of starboard.

The only thing to keep in mind is that a poly tank will increase in size slightly when you fill it with gasoline.
This is a permanent increase so you need to account for it when you install it.
Its approximately 3% in all directions.
i.e. dont install the tank so tight in the coffin that when it expands it will crack the fiberglass.

[Beaver]

Thanks for the feedback guys.

I took the hatch off yesterday and it was shocking! Three holes in the top of the tank, nasty mold and shmeg...guess I know why I was getting water in the tank. After seeing this I feel a lot better about doing the job. It also makes me appreciate that the coffins are sealed (AKA not leaking fuel into my bilge).

Hey Zachary, my FT4037 has about a 2 1/2 inch raised portion for the hose connections that at first glance makes it look like I am going to have to cut into the bottom of the hatch to make it fit. Did you have to do this? I have only removed the hatch so I haven't had a chance to dry run it yet.

Thanks again.

Rob

[erebus]

Originally Posted by Beaver

Hey Zachary, my FT4037 has about a 2 1/2 inch raised portion for the hose connections that at first glance makes it look like I am going to have to cut into the bottom of the hatch to make it fit. Did you have to do this? I have only removed the hatch so I haven't had a chance to dry run it yet.

I didn't have to do any custom fab for tank clearance.
I did however at the same time replace the coffin lid in its entirety because the previous owner had hacked up the original to access the rotten holes in the top of the original tank.
Pieces were missing and the core was a rotten soggy mess.
Just threw it away.
New piece of 3/4 coosa board which I glassed all over, dropped right in over the new tank.

Only thing I would have done differently when I installed my tank, is I would have put a drain in the aft end of the coffin. like a thru-hull or summat into the aft bilge.
The coffin is "kind-of" sealed from the deck, but the hole for all the cables and wires under the console went in to the side of the coffin on my 18' a little bit. So not perfectly sealed.
Whenever I'm hosing the deck down I worry that water is running down the cable hole and into the coffin.
With nowhere for the water to go I could be cruising around with a hundred pounds of water in there.
Cant verify that tho without taking off the console and coffin lid.

A few years ago I built a "dam" out of starboard around the hole in the deck to keep any extra nuisance water from draining down there. But I dont know for sure that its not already full.
Might try and drill a hole from inside the bilge and see.
Dont want to poke the new tank though.

[Beaver]

Thanks Zachary. I was thinking about putting a drain hole in the coffin but after seeing that my tank had 3 holes in it I'm glad that I didn't have fuel flowing down to my bilge. I was thinking it might make sense for me to put a sealed deck hatch above the area aft the tank. This would allow me to get any water or fuel out of it in the future.

When you braced your tank did you brace the bottom since only 8' of the bottom is supported?

Thanks.

Rob

[erebus]

Originally Posted by Beaver

When you braced your tank did you brace the bottom since only 8' of the bottom is supported?

I think I cut some starboard into wide wedge shapes to help support the angled parts of the bottom of the tank, and some fore and aft cleats to keep it from shifting.
There was also some aluminum angle in there too, but I cant remember what for...
Maybe I used it across the top on the sides to help hold the tank down?

It was about 4 years ago now, and of course I have no pics...

¯\_(ツ)_/¯

[Beaver]

By the way, I did a dry run with the tank (FT4037) and it fits perfectly.
What a relief.