Built in fiberglass side tank leaks

Caddy_Kid

Petty Officer 2nd Class
Joined
Nov 18, 2005
Messages
113
I have a 1970 Stevens 16' runabout with two built in side saddle tanks on either side of the hull by the seats. They wernt plumbed when I bought the boat, but after much work they function like they should now.

Havent had a problem in the past few trips, but the last time (after threading carefully thorough too many of those damn wake board boat wakes) I notice that the starboard tank is seeping fuel from between the hull and the tank. Since its not on the outside seam I cant easialy get to it, nor even see it. I have pondered what to do:

1. Get some of that gas tank epoxy coating that you use to seal a rusty car tank and pour that on the inside of the tank and hope.

2. Make a dam at either end of the tank between the tank and the hull and pour some resin in and hope.

3. Cut a hole large enough to get my hand through in the side of the tank and patch it from the inside with fiberglass and resin.

Has anyone else fixed something like this? The tanks are glassed to the bottom of the boat, so not really removable. Thanks,
 

JasonJ

Rear Admiral
Joined
Aug 20, 2001
Messages
4,163
Re: Built in fiberglass side tank leaks

If it were me, I would search for a set of polythylene replacement tanks and cut those fiberglass tanks out and never look back. they make the poly tanks in all sorts of sizes and shapes. The main reason I say this is the steady introduction of the new gas/ethanol blends. The corn gas eats away at fiberglass tanks, not a good thing in a boat. The poly tanks are impervious to the corn gas and will last longer than the boat will. When is comes to fire, I have a hard time justifying not spending the money to be safe. I had a steel tank in my boat and it started to seep at a seam. A new poly tank was in its place minutes after the UPS truck dropped it off. Good luck....
 

Caddy_Kid

Petty Officer 2nd Class
Joined
Nov 18, 2005
Messages
113
Re: Built in fiberglass side tank leaks

That was my other option. I had heard about the new gas eating away at the tanks eventually. I did look at Tempo tanks, they have close to the right taper, but are much too large (my current ones are a little over 10 gallons, Tempo's start at 18 gallons). Do you know of a good place to look for such things? Thanks.
 

JasonJ

Rear Admiral
Joined
Aug 20, 2001
Messages
4,163
Re: Built in fiberglass side tank leaks

overtons.com has tanks as well. I am not sure of your layout, but you don't necessarily have to have the fuel tanks where they are now. There are bow tanks, under floor tanks, all sorts of ways to do it. Weight distribution is another factor. For example, if you are stern heavy right now, or having trouble keeping the bow down at speed, a more forward position for the fuel tank is warranted. If in fact you are bow heavy, then moving the fuel to the rear can be done. You are not limited to where they are now. Good luck....
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,074
Re: Built in fiberglass side tank leaks

Brian, In answer to your original question - how to repair. You need to drain the tank, sand down the area of the leak to clean fiberglass, and wipe it with acetone. Now mix up some Marine-TEX and smear it over the area that leaks, plus as large an area around the leaking area as is practical. Now embed a piece of fiberglass cloth or mat into the Marine-TEX and smear more Marine-TEX over the exterior of the cloth/mat. Let it harden a day or two. I fixed my steel tank in this manner, and it has lasted several years (still not leaking).d:)
 

Caddy_Kid

Petty Officer 2nd Class
Joined
Nov 18, 2005
Messages
113
Re: Built in fiberglass side tank leaks

Great, I have some things to look for on Monday. I just gor back from a vacation to my parents 46' Chris Craft, or I would have had a chance to look at the tanks listed.

As my boat is set up now, the tanks are right in the middle of the boat, next to the seats. The boat is only 16' long, and has to be trimmed all the way down (really a bit more "glued" in than I would like) or it porpoises. I have the battery all the way forward, so I would think that I need more weight forward to get the bow down, and then raise the trim on the motor. But, one thing at a time. I just wish the leak wasnt on the side of the tank that I really cant even see without a flashlight and a mirror.
 

Caddy_Kid

Petty Officer 2nd Class
Joined
Nov 18, 2005
Messages
113
Re: Built in fiberglass side tank leaks

I just read an article on oldmercs.com from Mercury that said ethanol disolves one of the resin compounds in older fiberglass tanks and carries that away to the engine, weakening the tank and creating havoc in the engine. So I'm reluctant to spend time and money on a tank that will probably give me problems in the future.

I have been looking around and cant find anything that will fit exactly where my side tanks are now. But have stumbled on "pillow fuel bladders". I'm wondering if I could have two made that fit inside my current tank shells and then plumb them as though they were perminant tanks. Anyone tried something like this? Thanks.
 
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