POLY REPLACEMENT FUEL TANK

[Anonymous]

I want to replace my original 73 gal. aluminum fuel tank on a 1981 Aquasport 20 WA .Ethanol is the enemy . Has anyone used a  polyethelene replacement tank that will fit in the coffin ? I will go smaller down to a minimum of 50gal.?, as my 1992 Johnson looper 175 hp likes to drink fuel. I am in the Northeast ( L.I. N.Y. south shore ).Has anyone heard of coating an aluminum tank to protect against ethenol corrosion ? Thanks Gman.

[Capt. Bob]

I just replaced my tank on the 91 WAC.
I played with the idea of a poly tank and spent a good deal of time with the Moeller people on the phone.
It goes without saying, you need to do the math on getting a poly tank to fit your space. I wanted to reduce the size of mine (and I did).
In the long run though, I had an aluminum tank built. Why?

Well, with the WAC, I was worried that permeation, that comes with all plastic tanks, could possibly work its way into the cabin. I just did not want to smell gas in that enclosed area. If I was doing it for my CCP, I would seriously consider the poly. This would be strickly to reduce the chance of corrosion on the exterior/bottom of the tank.

I have not heard that ethanol itself causes corrosion to either poly or aluminum. Water trapped against the tank seems to be the big culprit.  

The upside of the aluminum is that it can be built any size you want. Proper installation will increase longevity. I can't recall any tanks that have been replaced on this Forum as having failed from the inside out. Doesn't mean it hasn't (couldn't) happen.
I'm not worried about ethanol fuel inside the alum tank. I worry about the water it tends to attract so I counter that with a separator.

Good luck.

[wingtime]

I replaced the tank in my 20' walk around with aluminum tank.  If you search my screen name you can find the thread with pics of the project.  I can tell you I cut open my old tank and the inside was like new.  The outside was the problem due to water being trapped against it under some foam tape a PO had put in.   I don't think the ethanol will effect the tank.  Ethanol fuel presents all kinds of problems but most of it is attacking rubber and a short shelf life.  I would recommend you drain your tank at the end of the season to prevent the fuel from going bad.

BTW I searched around for a poly tank option and I could not find one that fit the space to my liking.  

The original tank is about 24" wide on top  20" wide on the bottom, is 11" tall and 72" long.  If you do the math that will hold 75 Gallons but I think they subtract a few gallons for air space so they call it a 73 gallon tank.

[Skoot]

Im also going to be replacing my 35 year old aluminum tank very soon with an new aluminum tank. Im not sure of the overall condition, but I know there is rust/gunk inside the tank, which means there is or was water in the tank.  Another problem with ethanol is that it acts as a cleaning solution. So if your original tank had fuel with MTBE the varnish deposits from the fuel which accumulate on the side walls of the tank are now being cleaned off by the ethanol and mixing in with your fuel.

Ethanol does in fact attract water/moisture, but there are way to help combat this effect.  One is to keep your fuel tank full, especially when not in use.  Install a 10-micron water separator.  Dont let the ethanol fuel sit too long, it goes bad fast.  Lastly add some fuel stabilizer to help with phase separation.  I found this newer product called Sentry.  Its a fuel stabilizer and it also encapsulates water with a combustible so it can be burned off.  I tested it myself to see if the claims were true. I used a glass jar  a 1/2 oz water, 3-4 oz fuel and 1 oz of Sentry and shook it up.  The water disappeared/blended with the fuel. 2 weeks later there was no separation of water/fuel just as stated by the company.  Did the same test with Stabil marine and the water remained on the bottom and fuel on top.  Maybe snake oil, maybe not, But it sure seems to do what it claims.

http://www.sentrytreatments.com/

http://www.sentrytreatments.com/sentryv ... sentry.mov

http://www.sentrytreatments.com/sentryv ... erburn.mov

[Capt. Bob]

I replaced the tank in the CCP in 96.

We switched over to ethanol in Tally for good last year. I avoided it for as long as possible but have been using it for some time. I have been changing fuel filters twice a season and I notice the gunk from the inside of the tank trapped in the filter. I figure if I use ethanol long enough, I'll have a new looking tank inside in a couple of more years.

The new tank in the WAC has two pickups installed. One is for the motor and the other is for draining. I plan (and already have) to drain the tank after two months of non-use. Ethanol or other types of additives are a fact of life. We boaters just have to learn to deal with it.  :x

[Skoot]

I plan (and already have) to drain the tank after two months of non-use.

What did the fuel look like when you drained it?  Did you use a fuel stabilizer?

[Capt. Bob]

We plan on draining the CCP this weekend.
I've used Seafoam in this (CCP) tank. Don't know if it helps.

Just a followup:

Last weekend I drained my 13 yo CCP tank. The fuel appears to be in far better condition than what was removed from my WAC.
I'm not surprised. Why?

Well the tank in the WAC was original and I have no idea how the PO treated his system (though he stated he added stabilizer).
While my CCP tank was old, we have been on E-10 for over a year up here and it does dissolve the varnish left on the fuel surfaces.
I have been changing my filter/separator cartridge twice a season because of the debris coming from the tank. I also used Sea Foam as a stabilizer/additive and it appears to work very well.
So I'll continue down this path on the WAC and see how she runs.

As to use of a poly tank, I see no reason not to install one (if the space is available). As I stated above, I didn't want to chance a faint fuel oder in the cabin.
Good luck.

[dbiscayne]

I replaced my tank about a year & a half ago with a Moeller poly tank, 55 gal, under the deck in a center console, haven't noticed any fuel smells in the bilge, no problems so far.  You do need to leave some room around the poly tanks for expansion.