Odor from Diesel saturated plastic fuel tank

[Roc]

I've come to the conclusion that the smell of diesel fuel I notice is due to the odor that is imbedded (saturated) within the walls of the plastic fuel tank.  The odor is not of 'combusted' fuel, i.e. exhaust.  There are no exhaust leaks detected.  After motoring, the engine bay does not smell at all.  What smells is the aft cabin and aft storage lockers of diesel fuel.  Pulled the panels out of the aft cabin and no leaks are found on the tank or fittings.  However, the tank walls had a very strong fuel odor.  The odor is most apparent after a re-fuel or when the boat bounces around under sail, a result of fuel sloshing around the tank.  Never noticed this the first couple of years with the boat, probably because it took time for the plastic tank to get saturated with the odor.  Has anyone noticed this??  I'm thinking that Catalina may have had a poor batch of fuel tanks, sub-par resins used for diesel fuel containment??

[Ted Pounds]

Interesting.  Most of the earlier 34's (like mine) have aluminum tanks.  They only smell when they corrode through and start leaking   .   You could switch to a metal tank, but at over $300 it's a pricey way to solve the problem.   Give Catalina a call and see what they have to say about it.  Good luck.

[Ron Hill]

Roc : If there are no leaks like you say, I'd definitely call Gerry Douglas and register your complaint.  
See what he says and keep us posted on the outcome.  

[dhagen]

I have a 2001 Catalina 34 and have just come to the same conclusion.  Did you call Catalina?  What did you find out?  I sent them an e-mail, but have gotten no response.
Dan Hagen

[Stu Jackson]

Dan, as you'll fidn out, Catalina just doesn't do email well at all.  Suggest you use the telephone as Ron suggests.  I combined your two other individual posts, and you may want to consider copying them here and deleting the other one I combined, since it's pretty much the same subject.

[dodgercc27]

I have a 1989 Catalina 34 and I have the same problem.  I have a strong diesel smell in the cabin area of the boat.  I can smell it everywhere really. In the aft cabin, the main salon and so on.  I've checked for leaks and found none...my fuel level is stable.  It is not a burned diesel smell.  I've checked the vent to see if it was clogged with spider webs, but that was not the case either...like I said I can smell the fuel in the cockpit area, blowing up what I believed to be from the vent.   Is this a common problem for people?  I just bought the boat in August, so I'm still trying to figure her out. 

[Ron Hill]

dodger : Your year C34 came with an aluminum tank, so unless a PO changed to a plastic tank -
I'll guess that you have a fuel leak !?!
Don't discount a fuel lines, bad connection/clamp or gasket on the tank top !?!

Take off the port side panel in the aft cabin and you'll be looking at the fuel tank.  Inspect it and see what your problem is !?!  A few thoughts

[lazybone]

Check your plastic tank for a permantly affixed registration plate.  All permanently mounted below deck fuel tanks have to be approved.
If there's no plate you could have a PO installed who-knows-what cheap substitution.

[Peggie Hall]

Plastic fuel tanks DO NOT PERMEATE.  However, what you have may not be a fuel tank.

There are two different types of polyethylene--linear and cross linked.  Water and waste tanks are linear PE, but plastic fuel tanks MUST be cross linked PE because petroleum will permeate linear.  Plastic fuel tanks must also meet certain standards--no surface on which liquids can pool, fittings must be in the top, etc--and must be USCG certified.

Most people don't know any of this, so they replace metal fuel tanks with the plastic tanks made to hold water or waste.

If all the boats experiencing odor from permeated tanks originally had metal tanks, there's a good chance that's what a PO has done.  There are only few plastic fuel tank mfrs...Tempo, who was the biggest, has gone out of business (or maybe only stopped making fuel tanks)...Kracor makes/made a few, but mostly water/waste...I THINK Duracast made fuel tanks, but they also mostly make water/waste...can't think of any others at the moment, but there are a few.   Look for mfr label or embossed logo...mold #...anything that might help ID who made the tank. If it's a Ronco tank, it's definitely NOT a fuel tank...Ronco doesn't make fuel tanks.  Other clues:  Are all the fittings on the top and are they proper fuel fittings or do female fittings  have adapters?  And, look for the USCG certification label.

If you determine that the tank IS a fuel tank, you can rule out permeation...start hunting down the real source of your odor.  Start by clean the tank and every inch of hose and nook and cranny thoroughly with plenty of detergent degreaser, followed by a VERY thorough rinse...and then spray every surface nook and cranny with PureAYRE...then watch for odor to return .  Since diesel isn't a bacteria generated odor, it you'll smell it in cold weather just as much as hot weather, so this can be a winter project.

If you can't prove that the tank is made to hold fuel, it should be replaced.

[chuck53]

Peggy,
As always, you are a cesspool of information (pun intended).
Glad you contribute to this forum.  I always learn something from your posts.

[mainesail]

Plastic fuel tanks DO NOT PERMEATE.  However, what you have may not be a fuel tank.

Peggy,

I have heard you say this before but I have personally smelled it before on a true cross-linked tank so I would guess there may be varying levels of quality in "cross-linked" construction..

Below is direct from Moeller Marine. They are what Tempo became and are one of the larger makers of cross-linked fuel tanks.



1. The cross-linked polyethylene is inert, which totally eliminates any rust or corrosion problem. Cross-link polyethylene provides a longer life cycle and less weight than metal or aluminum tanks. Non-ferrous tanks (aluminum) can be subject to "oxygen starvation" which causes corrosion. This is usually caused by excess water being trapped on or under the aluminum tank surface.

2. All of Moeller's cross-linked thermoset plastic fuel tanks are one-piece seamless construction. This eliminates the pin-hole leak problems associated with metal or aluminum tanks, where welding slag is dislodged from the welds causing pin-hole openings. In addition to the features listed above, cross-linked thermoset plastics fuel tanks offer a wide variety of customer configurations not available in metal or aluminum fabricated tanks. Also the thermoset material can be blended to produce different colors, or processes altered to
produce Moeller's "low-perm" Fuel Tank.

What is "low-perm"? This is a new innovation offered by Moeller Marine Products to address the pending regulations being drafted by the EPA – Environmental Protection Agency and CARB – California Air Resources Board. The drafted regulations are centered on fuel permeation related issues associated with current marine fuel systems and associated components. Moeller's "low-perm" Fuel Tank will provide an environmentally friendly fuel tank that greatly reduces the amount of fuel permeation into the atmosphere. The question that has been raised by many of our customers is; what is fuel permeation? Permeation is the process by which smaller hydro carbon molecules pass through the chemical chain of the cross-linked polyethylene. That permeation can be described as a "wicking effect". Fuel odor is the end result of this process; note this is a normal occurrence in plastic fuel tanks and should not be confused with fuel vapor.

Permeation Key Drivers:
1. Storage temperatures increase the permeation rate: for every 50 F / 10 C (degree(s)), the rate doubles.
2. Pressurized fuel tanks will increase the permeation rate.
3. Ethanol Blends will increase permeation rates.


The fuel permeation levels from current tanks are higher than the drafted regulations, thus the introduction of the Moeller's "low-perm" Fuel Tanks.

Moeller's "low-perm" Fuel Tanks utilizes Moeller's trade secret processing techniques. This is the solution for meeting stricter EPA / CARB Fuel Permeation Regulations set for 2011. Moeller Marine Products is leading the way in the industry by providing the first recreational marine fuel tank for testing at CARB. Moeller's "low-perm" Fuel Tank has surpassed expectations and is the solution for the industry.

Moeller's "low-perm" Fuel Tanks offers the following:
• Unique composite structure
• Ultra-low permeation to fuel –meets proposed levels
• Excellent permeation resistance to higher alcohol contents fuels
• Two layer composite system with excellent adhesion
• Excellent impact and toughness

This is where our innovative concept provides Moeller Marine Products a competitive advantage. Please contact us today to discuss our solution with you.

The time lines for the drafted regulations are as follows:
• Fuel Hoses – Jan 1,2009 ( Perm rate equal or less than 15 g/ m2/day)
• Self Sealing Cap (Portables) – Jan 1, 2010.
• Primer Bulb and Marine Tank (Portable and Permanent) – Jan 1, 2011
o (Perm Rate for Primer Bulb equal or less than 15 g/ m2/day)
o (Perm Rate for Marine Tank equal or less than 1.5 g/ m2/day)
Please use the following websites to stay informed versus the regulations and time lines:
www.arb.ca.gov/omt/omt.htm
www.epa.gov/otaq/marine.htm

[Peggie Hall]

Good info, which I'll add to my files.

Mfrs never say "never" or "can't happen" or "always" or "completely" (I learned that the hard way when I made a claim for one of our products). So Moeller would never say their cross-llinked tanks are impermeable...they're "low" perm.   Wall thickness is a factor and quality can vary some, but USCG standards keep it from varying enough to be dangerous. 

You say you've smelled permeated cross linked poly.  Maybe...but I've yet to smell a permeated holding tank.  I have heard from people who swear they had a holding tank that permeated...and as "proof" cite a tank they removed from their boat and stored in the garage...and the whole garage reeked. But invariably it's turned out that the tank had NOT permeated...the source of the odor was the inside of the tank because there were no plugs in the fittings.

I've contributed all I have to offer to this discussion...fuel is not my area of expertise and I've told y'all everything I know. I had to learn that much because I had to explain to our customers why they couldn't replace a fuel tank with a waste/water tank.

[Ron Hill]

Guys : It'll be interesting to hear from back from "dodger" and find that he has a metel fuel tank!!
 
Anyway all of this link and cross link discussion was really great !!   

[mainesail]

You say you've smelled permeated cross linked poly.  Maybe...but I've yet to smell a permeated holding tank.  I have heard from people who swear they had a holding tank that permeated...and as "proof" cite a tank they removed from their boat and stored in the garage...and the whole garage reeked. But invariably it's turned out that the tank had NOT permeated...the source of the odor was the inside of the tank because there were no plugs in the fittings.

I have yet to come across a holding tank that permeated either. Usually it is the hoses though I have seen some where the plastic welds failed and it was letting the stink out near the failed weld.. I had one in my barn for months, up in the attic where it gets very hot. I had put PVC plugs in the tappings to control the odor. I went up there one day and it was blown up like a blow fish, it was hot and sealed, but no odor.. I think the difference is the hydrocarbons in the fuel vs. no hydrocarbons in waste. Still confused as to why a PO would replace an aluminum tank with a poly tank..?? Catalina's replacement tank prices are impossible to beat, I know, I installed one in my C-36 for a LOT less than the custom made tank I just did on my CS-36..!

[dodgercc27]

Sorry for the delay, it took me a while to get down to the boat.  I thought I had a metal fuel tank, but I wanted to be %100 sure.  I confirmed tonight that I in fact do have a metal fuel tank.  So regardless of the recent and interesting discussion of plastic fuel tank designs, I still have a odor source that I have to eliminate.  As mentioned before, I do not have a leak in my tank, as I have never found any evidence of fuel in the surrounding area or bilge.  I'm going to have to do an inspection of the fuel lines. 
The search continues.