Dramatic improvement in fuel quality due to change in winter storage procedure

[Breakin Away]

In this message from late 2019 I mentioned that I was considering emptying my fuel tank during winter layover:

https://c34.org/bbs/index.php/topic,10409.msg80510.html#msg80510

I was unhappy with the quality of my diesel fuel, and with the frequency with which I had to replace my costly spin-on Racor filters. I tried a number of things to improve the fuel (I use Biobor and Star Tron Enzyme at the recommended dosages), and now I think I've finally found the answer.

After emptying my fuel tank for the past for four winters, I am happy to report a dramatic improvement in fuel quality. My current Racor filter is now over 25 months old (and destined to last even longer), already about double the age of my prior filters that plugged after about 13 months. I was getting a little nervous for waiting so long this time, so last week I disassembled it and had planned to replace it. However, the filter was pristine (see picture) so I'm leaving it in for another year..

Some history from my engine log documents the improvement in fuel quality:

• My first Racor filter plugged on 7/19/2017. I aborted a planned overnight cruise, sailed home, and limped back into the slip at low RPM. The filter was 13 months old. I replaced it and the secondary fuel filter.
• Replaced Racor filter proactively on 8/18/2018 (13 months old). Upon inspection, I could see that it would have clogged if I waited much longer, since the pleats were filled with gray-black stuff.
• Racor filter plugged on 9/28/2019. I aborted a planned overnight cruise, sailed home, and sailed back into the slip. The filter was 13 months old.  I replaced it and the secondary fuel filter, as described here.

Up to this point, I had dutifully topped off my fuel tank every fall, following the traditional logic that eliminating headspace would minimize breathing and condensation and help preserve the fuel through the winter. For 2019 winterization, I decided to try the opposite, and ran my tank down as far as possible during the season, then drained the remaining diesel from the tank into jerry cans for storage at my home.

• For spring commissioning in 2020, I siphoned the fuel back into the tank, filtering through a Mr. Funnel fuel filter (which claims to remove water along with particulate contaminants). I operated the entire 2020 season without a fuel filter incident.
• At the end of the 2020, 2021, and 2022 seasons, I again ran the fuel down to 5-10 gallons at the end of the season, and drained the tank contents into jerry cans for storage at my home. Upon subsequent spring commissioning, I again siphoned the fuel back into the tank through a Mr. Funnel filter at the beginning of each year.
• I had replaced the Racor filter (and secondary fuel filter) proactively on 4/24/2021 as part of spring commissioning. The Racor bowl remained pristine for the entire 2021 and 2022 seasons and so far this year. The filter that I show in the photo below is the one that I installed in April 2021 and will remain in place.

After 3 years of a control experiment (topped off fuel tank for winter), and 4 years of testing the alternative (drained fuel tank for winter), I conclude that the storage of the fuel in sealed containers during the off-season is the reason for my dramatic improvement in fuel quality.

[pbyrne]

I'm sorry I missed your original post.  I'm 1534, our boats were sitting next to each other when they were built!

I can tell you that I have an aluminum tank.  There is at least one deck plate in the port locker, and from memory the tank is a tight fit.  I have a photo somewhere, but I can't seem to find it...

Considering removing the fuel for storage solved the issue, what do you think was happening?

[Breakin Away]

It's very odd that you have an aluminum tank, yet were only one boat before me. I have plastic, and one added incentive to empty the tank every winter is to reduce the exposure time that could lead to eventual permeation of the diesel odor through the plastic.

Have a look at this post: https://c34.org/bbs/index.php/topic,10409.msg81154.html#msg81154 . In addition to my tank being plastic, it's mounted much higher than the others shown there, with virtually no head space over top to allow for easy removal. To get it out, I think I'd have to tear out the wood above it from the lazarette (since the access ports probably don't provide sufficient access to fastener hardware), remove all the top fittings, and then barely slide it out the opening. And it makes it virtually impossible to install a "stock" aluminum replacement because it probably would not fit.

If/when you get a chance, please have a look at the dimensions and location of your opening and post a picture. It would be interesting to compare. Do you think a PO might have replaced your original tank with a (custom?) aluminum tank?

As for the root cause of the fuel improvement, it could be several things. Storing the diesel in a well-sealed container helps. Minimizing the amount stored and keeping my partially filled fuel tank turning over faster keeps the fuel fresher. And filtering virtually all the fuel into the tank once a year helps. I can't predict which of these is the dominant factor, but taken together, the end result is a night-and-day difference.

I'll mention that Maine Sail used to have a lot of detailed information on his site demonstrating that topping off the tanks provides little or no benefit. So my findings agree with his prior statements.

[pbyrne]

I will check for a photo again... I just can't find it at the moment.   

But... from memory I think I have the same 'shelf' you do.  I remember thinking 'how am I going to get to the top of that tank to inspect it?'.  There is a board and deck plates over the tank in the port cockpit locker, so I resigned myself to opening that up some day.

That shelve is interesting... why would they do that?  It also preculdes a larger tank, which would have been a nice option.

[pbyrne]

Found them.  They aren't side on exactly, because I was trying to get some pics of what was in there.

None the less they do show the deck plates, and how close the tank is to the locker.  I'm 100% confident I have the same arrangement you do.

[Breakin Away]

Thanks, that is very helpful. That tank was fabricated by Ezell Industries in Perry, FL. https://ezellindustriesinc.com/

I'm not at all sure about this, but it's possible that your boat may have originally had a plastic tank that was later replaced by a custom-made aluminum one. I'll have to keep Ezell in mind if I ever need to replace my tank.

[pbyrne]

Thanks, that is very helpful. That tank was fabricated by Ezell Industries in Perry, FL. https://ezellindustriesinc.com/

I'm not at all sure about this, but it's possible that your boat may have originally had a plastic tank that was later replaced by a custom-made aluminum one. I'll have to keep Ezell in mind if I ever need to replace my tank.

It's possible of course, however based on what I know of the PO, I'm not sure.  When Catalina does put in aluminum tanks, do they use Ezell?

[Breakin Away]

I saw a note in another forum claiming that Catalina uses Ezell. Since I read it on the internet, it must be true. 

I'm not at all unhappy with my plastic tank. I think it's more corrosion resistant. I read somewhere here about some people complaining about odor permeation of the plastic tanks, but I have not noticed it. Neither has my wife, who is extremely sensitive to smells.

It's not particularly important to me, I was just curious. I believe that around that time aluminum was in short supply and prices for it were sky high, which I've heard is why they switched to plastic for awhile. It's also possible that Catalina offered a choice, with an upcharge for an aluminum option. Or maybe your PO complained about permeation and got a warranty replacement to an aluminum tank.

[Noah]

The MKIs came with aluminum fuel tanks. Why don't you just post a question here to all MK II owners; "Do you have an aluminum or plastic fuel tank?"
Catalina Direct used to sell Ezell replacement aluminum tanks but two years ago switched vendors after a business dispute.

[Ron Hill]

Breakin & Guys : Catalina parts stopped stocking the plastic fuel tanks for MK 1 boats because of fuel permeation. I always thought it was a good idea, BUT!!

Don't know who the supplier was for those early plastic tank, but I 've talked with Owners and they affirm the diesel smell !!

A few thoughts