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Fuel Tank Coffin

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My feelings are let gravity be your friend. That way, anytime the boat is on trailer and the bow raised, any water will drain out. With a pump, you have to remember to turn it on and off. Also, I do not like the idea of pumping gas through an electric bilge pump should a leak happen while on the trailer.

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Now i,m a little confused. I was ready to drill a drain through the rear bulkhead. I ran a rod through the garboard drain to cofirm there was a clear path from the coffin area. The rod I was using was 8' long. I was able to drive it all the way in,which means it was under the coffin area. So, should the drain be installed in the bottom of the coffin?

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On a side note, I was suprised how much water was trapped in the inner hull. After I pulled the rod out water drained for a long time. Today I repeated the process and more water came out.

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Your fish box (if you have one) and your fuel coffin do NOT contact the hull of the boat, but in fact float about 4" above it. So, your rebar or rod simply pass right under. For me.. I'm torn a bit on the putting a drain in the coffin. I like knowing whatever is in there isnt going any further. However, I think dan makes the most important point about trapping and possibly pumping fuel. Other then condensation, water should not be getting in your coffin unless you have not properly sealed your coffin cover and the access covers on it. If I were to drain mine I would want to run an actual line back to a true bilge area the would have to be created. Which is a bunch of work! I guess another school of thought might be that hey, it's already wet in there (hull/foam) to some degree and simply allowing the water (condensation) to run out into a channel in the foam and ultimately out a Garboard drain may be all anyone needs.

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I'm kinda torn also,but I put a stainless tank in a few years ago thinking my fuel tank issues were going to be a thing of the past. well due to the water issue and electrolysis I had to pull tank and repair(again!) The deck plate could have been part of the problem but i don't want to do it again.Secondly what caused the electrolysis ? fuel guage? grounding?

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There are a few reasons for the corrosion and it does have to do with electrolysis from the gauges . Also it is in a sealed dark area and it will always be damp in it and water can also make it's way in there if the fuel fill ,vent, and motor fuel lines are not totally sealed off as water getting into there from the deck wether it is rain or saltwater intrusion.

To Drain Or Not TO Drain. First off I sure don't want to be on a boat when the bilge pump in the coffin is turned on and there was a gas leak in there. If one wants to pump water out I would say a 4" inspection plate at the center rear of the fuel hatch and you could use a hand pump every once in a while .

 

Thats my 2 cents worth. captain.gif

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I've been giving this one some thought since someday I too will replace my tank. I feel that as long as you seal the top of the foam, you can avoid the condensation issue by leaving the pie plate in the hatch (inside console) open when you're not using the boat, it should be able to dry out in there. Sealing the foam with a layer of fiberglass tape will keep the moisture on top of the tank. What's everyone's thoughts on that? I'm more concerned about a catastrophic tank failure filling the bilge. One cycle of the pump could set off a serious explosion since the semi sealed bilge would not only have liquid fuel but vapor as well, essentially turning your Robalo into a bomb.

Also, consider the age of these boats and the fact that the tanks have survived decades that, for many, have included sitting uncovered for extended periods. Today, we know to coat our tanks with coal tar or epoxy paint to prevent corrosion. Realistically, you're looking at at least another 20 years before having to worry about the tank again.

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I was thinking of just using my left over half a gallon of gelcoat and pour out over my foam and edges.... that should do it ?? is that what you are thinking

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Thanks for all the input, One thing needs clarification, this boat does not have a bilge or a pump. Everything would exit through the garboard drain. I'm still on the fence?

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Basketcase,

 

you are correct there is no bilge unless someone modified the boat and made one. Basically, your creating a channel with the rebar in the bottom of the hulls foam filling. If you drilled a hole 1" say in the back lower portion of your coffin and took the rebar and poked a channel down to meet the one you created with the Garboard drain...that's where the water is going.

 

No bilge, no pump, just a path for water to follow out when the Garboard drain plug is pulled and the boat is tipped back a bit.

 

Hope that helps clear things up.

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I have to say since we are on the subject, I ended up with a unique situation regarding the tank that takes all this out of play. I was OK going to a smaller tank then the original. By installing a 65 gal instead of a 110 I gained over two feet of space behind the tank, as I installed the tank forward. Since the tank was epoxy coated and a tight fit no foam was needed. I added a large hatch to provide access the rear of the coffin just behind the pedestal. By proper placement of the access plates under the console and the access hatch I added, have access to fuel fill, vent, sender, and line out. I can actually change all my lines without taking the console or coffin lid off. Not to mention, I just open that 12" x 27" hatch and I'm looking at the tank (well the back end of it at least. Takes condensation out of it, looking for fuel leaks are a no brainer and I gained additional storage space.

 

I guess where I was going there was, if you dont mind giving up a little fuel, even 20 gallons you can make the coffin far more accessible and less of a mystery as to what's going on down there. Wish I had a picture handy but I'm a long way from home as I type.

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getting ready to button up my new fuel tank on a 2160 but before i do i think i will route a siphon tube to the rear of the coffin box so that i can acess the tube from the deck lid so i can attach a bulb to siphon out any water

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That is a pretty smart idea, Markman. Sometimes the simplest ones are the best :thumbsup:

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Hi Larry and welcome to the site. Is your tank leaking?

 

Don't know the dimensions. See if the manufacturer's label is still on top of the tank (should be located next to where the sender unit is installed. If it is still there and has the manufacturer's name, contact them for the information.

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Is anyone still around on this thread that ended up installing a drain from the coffin box? How did you make out? I’m at that stage now, I bought a 72” 3/4” bit extension.  I have a bilge pump at the back near the drain plug. I have a 23’ 1978 CC with no in floor fish box. My new tank will be coal tar epoxied. I have some answers from 2-n-tow, just a coincidence I came across this thread and just wondering if anyone who posted is still around and ran the drain?

i think I will run the extension into the drain plug hole and see how far I can get before it hits something.

Edited by Retainer

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