Leaking fuel tank

Hi all,
I have a leaking fuel tank. It is at this point a very slow leak. I filled up almost a month ago and still have 12 gal. This is the standard 1988 25gal aluminum tank.

It appears to be coming from or around the front lower seam. I think it is being caused by water pitting, as it is the very lowest part of The tank.

My question, has anybody else had this problem? I’m wondering if I can clean the tank out and fill that lower area with epoxy. I think I know the answering to this second question, do I have to remove the engine to remove the tank?
Ugh!

Thanks

Hi Gary:

An epoxy repair to your tank will not last for any time; remember you must have completely oil free surfaces for the epoxy to hold. Worse than that is the knowledge that your boat has a weakness.

You can therefore choose to have the existing tank repaired and pressure tested professionally, or purchase a new tank.

Removing the engine is simple; apart from tools, the only things you need is lumbar to create a “Y” frame to support the boom, and comealong from home depot.

Use 3/8" line to create a noose for the comealong, and the stretch the comealong between the noose and the engine lifting point. (If you have two points, put a line between them, and connect to that line.)

Take off the top engine mount nuts ensuring you disturb the lower nots as little as possible.

Undo all diesel, water, exhaust and electrical connections, and lift the engine off the mounts. It is preferable to have a second person doing the comealong cranking on the deck, as you will need to bring the engine forward and clear of the bulkhead. Once out, rest the engine on planks across the cockpit, when you can clean it, and, if necessary, (some engines are temperamental) hug it.

Last time I took an engine out this way, it took 44 minutes from scratch.

Thanks John,
You are correct. That is the best solution. I just put a new engine on a year ago so I know the procedure. Although I doubt I can do it in 44 minutes.

So the question now is, where do I get a replacement tank? And is aluminum still considered one of the best solutions?

Thanx

Gary,
I think you should consider repairing the tank, although you might not know if that is possible until you get it out. It seems most likely that the leak is due to water at the angled bottom corroding the Al and that should be repairable.

While you’re at it, you might consider putting in an inspection port. I’ve always wanted one, maybe at the top of the port side of the tank? Another feature I wish we had on our tank is a small well (made of Al) at the tank’s bottom that would collect water that could then be drained off.

Our 1982 tank, mounted aft and above the engine, is probably similar to your 1988 model although ours holds about 32 gallons. The design does have the advantage of a low forward area that should collect water which settles to the bottom. Some years ago I made a gismo to try to suck out the water that may have accumulated. It consisted of a pulse pump and a Racor filter, mounted on some plywood, with brass on/off valves. I stick the input hose down in the tank and make sure the hose gets to the tank’s bottom. Some stiff wire tied to the hose helps. The 5 gal jug with the clean diesel is dumped back in, hopefully minus the water from the tank’s bottom.

I’m not sure if Al is still a good choice for fuel tanks, but probably any choice (SS, monel, plastic??) has pros and cons. Maybe others on the forum can address this question.
Dan Shaula BCC 59

Ahoy Gary , you have assumed correctly , that water has created pitting of the tank aluminum surface inside your tank , mine has that too .

Back in 1998 I installed two Clarus inspection ports in the forward tank side, one on each side of the centered fore n aft baffle .

These give fairly good access to the lower forward tank welds inside the tank.

Will try to attach a pic .

I installed these removable inspection plates to see the inside of the tank and to mop it out once a year .

I have noticed the water caused pitting making the tank bottom less smooth when rubbed with a cloth and a brown color staining on the aluminum.

Knowing what I know now , if my tank had a leaking problem , I would try the various fixing methods first before making the decision to build another new tank out of Monel .

The Clarus made ports may not be available any more , but they would be easy to fabricate with a drill press , and jig saw . I used my Bosch jig saw to saw the large holes in the tank on the boat .
The nitril or buna-n-rubber gaskets do a great job of not even any diesel leaks or seeps at the plates , they have worked great for my purposes some 17 years , already .

Clarus has an illustration of the split backing ring insertion and diagram of how to install them , this illustration is in my puter files somewhere , and I can find it , if you need it .

Thanks guys, this has been really helpful.

I am now leaning toward installing 2 inspection ports on the port and starboard sides of the tank. I have good access to both those areas. Then I will clean the tank thoroughly and coat with an epoxy designed for this application. if I had ordered a new tank i would have had it coated anyway. And the only place the tank appears to be deficient is at this lowest part. I think a repair will be actually better than a new tank w/no coating.

Of course I will probably change my mind again. but I think this solution has a number of very good points. If I open up the tank and find a lot of damage, then I will order a new tank.

FWIW , the Clarus Plate illustration is attached .

Here’s another brand to consider. Check out the video.

http://www.seabuilt.com/plates.php

This brand is carried by Fisheries Supply here in Seattle, our biggest marine store. A friend installed one of these on his diesel tank recently.
Dan