TOPIC: Molded Fiberglass Fuel Tanks

My newly acquired Power Cat 23T has two molded fuel tanks, to fit on each side just in front of the MERC i/o drive doghouse. The question is, has anyone had any experience with this style tank? I'm wondering if with age they may not be safe or may break down inside. The boat is a 1968 model. They look sound but just thought I would pass it through the vast knowledge forum. Thanks - Rich

I can't say about those tanks in particular, but I had a VW kit car that had the gas tank molded into the body. The tank was fiberglass as was the body. The car was probably 25 or so years old and the tank it still performed perfect. As long as the glass is not cracked or visiably deteriorated I don't think there would be any issues. Just my 2 cents!

Being a 1968 the fuel system in the boat is not capable of dealing with the ethanol in today's fuels. The ethanol can dissolve the resin leading to leaks in the tank. Also all rubber components of the fuel system (including the carb kits in the engine) will need to be updated to alcohol resistant components. IF, and it's a big IF, you have ethanol free fuel available everywhere you boat you can most likely use the existing fuel system without any trouble but is it really worth the risk.

I agree, if it is in good condition and you have ethanol free fuel you should be okay.

Ahh.. I didn't know about the ethanol issue. I'm gald this post came up!

There is no problem with fiberglass and ethanol. FIber glass tanks are what fuel is stored in under ground,have been use to store ethanol for years. Glass (FRP) tanks are better then metal in so many ways

Now the problem is the fuel line. You will need to change them to a newer type of hosing (fun)

newboatbuilders.com/docs/Ethanol.pdf

a short list of what is stored in FRP tanks
* Gasoline
* Jet Fuel
* AV-Gas
* Motor Oil
* Kerosene
* Diesel Fuel
* Alcohol-Gasoline Blend Motor Fuels
* Ethanol-Blend Motor Fuels
* Methanol Blends
* Oxygenated Motor Fuels
* Water & Septic, acids and caustics
* Any Gasoline/Ethanol Blend, including 100% Ethanol, Methanol or M85

Allan

Epoxy resin underground tanks. Installed about 130 of them.

My 1961 Powercat 18DC had molded glass fuel tanks. They were wretched smelling. Danny Ledger, son of Ray Ledger the founder of Powercat, said they were a dismal failure. I removed mine from the boat and got rid of them. Going with standard metal tanks. Danny said the fuel ate them up. Big difference between epoxy resin and polyester or vinylester resin.

Thanks for all the great input on the fuel tanks that came in my boat from the factory. The age and material used in these tanks and the alcohol fuels of today, will start me shopping for a set of tanks to replace them. A new fuel filter/separator will go in at the same time.
(right after this 5 inches of snow predicted tomorrow and a few months pass by) The forum wins again!!!! - Rich

[/quote]

WOW Crosby That CAT is looking so good! You do such fantastic work! WOW!

Brian - that Cat is over the top! It needs to be parked next to my JetFlite


RE the tanks - listen to the posts about Ethanol, as they are 100% correct. The tanks WILL slowly dissolve. Then you will have tiny bits of fiberglass being sucked into the fuel system. Naturally, when you least expect, your motor will get a bit of glass stuck in the carburator jet. Then you are dead in the water. Not fun, not worth the risk.

Just ask the folks with vintage skagits that had the built in tanks.... they all take them out.

It would be a disaster waiting to happen to keep your glass tanks. REPLACE THEM!!! Read the acticle so kindly attached in a previous post. It's pretty clear if you read the whole article that Polyester and gas with etahnol is a big NO-NO. I don't theink the person who posted the link and said it would be fine actually read the article. Underground tanks for gas are probably not made with polyester resins. It's too permiable. Epoxy is probably used, it has much lower permiability.
At any rate, stories abound of the gummy residue produced in older polyester tanks using new blended fuels rendering fuel systems and valve trains useless. even if you cna get ethanol free gas now, long term it'll be gone. Replace the tanks now while you are restoring rather than have to rip it apart later.
My two cents!!
Randy

I have a question on a related topic. A couple of seasons ago, I needed a third outboard motor tank for my boat, and all I could find on short notice was a three or four gallon red plastic tank at a BoatUS store.
I used the tank for one trip, and found it to have several shortcomings, and haven't used it since. One problem was the plastic screw-on cap. It screwed on and off easily before I put fuel in the tank. By the end of the day, however, the cap was binding so badly that it was very difficult to install or remove. I tried lubricating the threads with vaseline, and then oil, and then grease, but nothing helped.
I've since encountered this same problem with a couple of other plastic fuel containers, and I suspect the problem is a slight softening of the cap or tank material, leading to binding of the threads. Has anyone found a lubricant or other coating that prevents this binding ? I don't know if the fuel I used at the time contained ethanol .

That reminds me of a couple of chainsaws I have with plastic gas tanks. After the first year the caps or tanks expanded to the point that the cap was very hard to put on and off. A new cap fixed on but not the other. The alcohol fuels make the plastic swell and the longer it is in there the worse it gets. I now store them with the tank empty. This may apply to your tank. - Rich

I am a newbie here but this is one of my favorite websites and I have referred many people working on old boat to this site.

I am also the author of the article on ethanol (Much Ado About Ethanol) linked in a previous post.

3hulls, to answer your immediate question about why the caps get so hard to remove. Its because the tank expands when you put fuel in it. Those plastic tanks are made of cross-linked polyethylene (PE). PE is slightly permeable, that means a little bit of fluid (not enough to create a danger) permeates into the tank wall and then the tank expands by about three percent. Just enough to make the damn caps difficult to get off.

As for fiberglass tanks, it is not advisable to use FRP tanks for gasoline. Boat tanks are a little different. We let them sit for long periods full of fuel which allows the fuel to over time attack the tank. Yes there have been problems with those underground tanks. Especially when MTBE was put in gasoline. MTBE was leaking all over the country.

Any way, your tanks are so old they should be replaced. Buy some good quality Plastic tanks or aluminum tanks and they should last another 20 years.

Peter D. Eikenberry
newboatbuilders.com

When I was in the radiator bussiness we used to get a lot of rusted out leaking gas tank that could not be replaced of fabricated.
We would just clean them out and pour a gas tank liner into them and they would never leak again.

I do not see why the same could not be done to a fiberglass tank.

That would be a little hard to do when the tanks are molded into the boats that have them. Now if you can figure out a way to pick up the boat and rotate it as you would do with a gas tank from a car let us know.
Mike aka pathfinderz1

By the way, integral tanks are no longer permitted for gasoline powered boats. Haven't been allowed since 1977

33 CFR
Sec. 183.550 Fuel tanks: Installation.
(a) Each fuel tank must not be integral with any boat structure or mounted on an engine.

So they should be replaced anyway.

The Power Cat tanks were not actually integral. They were molded and then simply tabbed in place. Piece of cake to remove. Again, I refer you to the son of the manufacturer of Power Cat boats who reported they were a dismal failure and should be removed.

A lot of the kit-planes use this type of tank,,longeze,verieze,etc....Do a bit of research and you will find them very reliable

pathfinderz1 wrote:

That would be a little hard to do when the tanks are molded into the boats that have them. Now if you can figure out a way to pick up the boat and rotate it as you would do with a gas tank from a car let us know.
Mike aka pathfinderz1

Sorry
up until your post I did not realize the tanks were molded into the boat.