C34MkII fuel tank maintenance

[Breakin Away]

I'd like to consider doing some cleaning/maintenance on my MkII (model year 2001) fuel tank, and would appreciate some guidance for those of you who have done this before. How do you access the tank? It seems like might be glassed in on top, with only a couple screw-off ports in the port locker. I know that one of the ports covers the on-off valve from the dip tube. Is there a way to remove the dip tube?

Does the tank have any inspection ports installed at the factory? Is there a way to get to them without cutting apart the locker? Is there a side panel in the aft berth that gives any better access? What is the tank made of?

It seems like the fuel fill port is not a straight drop into the tank, so you can't insert a dip stick or pump-out wand into the tank. How else do you empty the tank?

[Dave Spencer]

Breakin,
I pulled my tank and cleaned it in 2012 per Ron Hill's Tech Note instructions.    Here's a link to a similar discussion.  http://c34.org/bbs/index.php/topic,9355.msg69451.html#msg69451 I have a 1994 Mk 1.5 but I don't think the fuel tank configuration changed much for later builds.

The tank is not glassed in.  It's screwed to the shelf accessible by removing the port wall in the aft cabin which comes out very easily (once you've cleared out "the garage").
The suction and return line tubes are threaded into the tank as shown in the picture.  The level gauge is bolted in via a small plate.
There are no inspection ports on my tank nor do I think there are ports on any C34 OEM tanks.  I seem to recall some owners have added them.  A search should show this.
My tank is made of 0.090" thick 5052 Aluminium
The fuel fill is not a straight drop.
The tank can be emptied by pumping it out. Have an appropriate number of 20 litre diesel containers available and disconnect the fuel delivery line after the electric pump and place the hose in the container.  For convenience, you will likely want to make up a longer hose. 

Pics of my tank In Situ and removed attached.

Hope this helps.  It's a fairly easy job.

[Geoffreykwright]

I'm in hull 1494 (2000).  I've never cleaned the fuel tank - not sure if the PO ever did.  I'm careful about putting in clean fuel (I've got a funnel with a filter).  My Racor does not indicate any sediment.  I don't think I am having any issues...engine is running fine (980 hours).  Nonetheless, is cleaning/inspection something that should be done periodically?

[Dave Spencer]

Geoff,
My tank was clean when I pulled it out. It was 18 years old and to my knowledge, had never been cleaned. Nevertheless, I went through the process because I had already gone to the effort of pulling the tank. I'm glad I did as I no longer lay awake worrying about nasty growth or sediment hiding in the tank waiting to clog my filter and kill my engine at the most inopportune time.

[Geoffreykwright]

Thanks Dave!  May pull it one of these years and do the same.  Just wondering if anyone recommends regular inspection.

[Breakin Away]

FWIW, I replace my Racor filter every year. I've never seen even a drop of water in my Racor bowl. But I do see a little bit of brown stuff there occasionally. I'd like everything to be pristine, so now that my tank is down to about 6 gallons in it I am considering draining it to inspect the fuel (or the tank, if there was an inspection port).

I usually fill the tank every winter to avoid "breathing" in the headspace and condensation that comes with it. That has apparently worked well because I don't ever have any water. But there is a little bit of stuff that I'd like to completely eradicate.

If you're way up north you may have a less hostile environment.

[Dave Spencer]

Geoffrey,
I think regular inspection would only be for the most anal sailor.  However, I think Breakin has a point.  I suspect those of us in the north would be at lower risk for growth inside the tank as opposed to those sailors in warm humid conditions for most of the year. 

[ewengstrom]

Interesting note. A dear friend with a 1988 C30 cleans his fuel tank on a schedule of every two years. This spring he drained the entire tank and then used a cloth wire tied to a stick to reach inside and actually wiped out the tank wherever he could reach to remove any residue. Pretty thorough eh?..... Well...just a few weeks later at the beginning of our annual cruise he was heading south on the Chesapeake when his motor died.....he sailed/was towed into the marina where three of us descended upon his vessel to help determine the problem (the first problem was there wasn't enough beer aboard...readily solved that one in record time)
As it turned out we found a clog of really gross stuff had worked its way into the pick up tube and had lodged right outside the secondary filter at a 90 degree elbow BEFORE the filter!!! The remedy was to pressurize the tank thru the vent hose with the other end disconnected at the filter. (easily accomplished with a paddle board inflation pump) A nice size glop of pretty ugly stuff plopped out into a paper towel and that and a new fuel pump was all that it took to get him going.
Interesting side note I just remembered. This good friend carries spares...he even had a brand new spare factory fuel pump he'd had aboard for about two years "just in case". The problem was that not only had the original fuel pump failed...but the spare was dead too!!!! (yes...we tested it extensively to come to this determination) We ended up having to get a ride to a local auto parts store to get a temporary diesel fuel pump so they could at least continue on for the week.
Moral of the story, don't clean just the tank, pressurize your lines a bit too and get them cleaned out prior to the secondary filter. Secondly, TEST your spare parts before you stow them. Replacements may not be so readily available and that would have been an ugly end to a fun week!!!

Eric Wengstrom
1988 C34 "Ohana" 

[Ron Hill]

Guys : I got the idea of cleaning my fuel tank came from my experience in aircraft maintenance!!  In Vietnam (especially) the UH-1 (Huey) on it's 10th PE (Parodic Enspection every 100 hour of flying) called for removing the fuel tanks (self sealing blatters) and turning them inside out and cleaning them.  Can't tell you how many gallons of fuel is used in 1000hrs, but it's a bunch!!  It didn't take that long in days to accumulate 1000hrs either.

Can't remember, but I think I first cleaned my tank at the about 10/12 years. I dutifully used Biobore and Waterzorb, but the tank still needed to be cleaned!!

A few thoughts 

[lazybone]

Geoffrey,
I think regular inspection would only be for the most anal sailor.  However, I think Breakin has a point.  I suspect those of us in the north would be at lower risk for growth inside the tank as opposed to those sailors in warm humid conditions for most of the year.

Boats in the "North" can experience large, quick swings in temperature which cause condensation within fuel tanks.  Our 34's have relatively small tanks which are easy to remove. So....Every ~5yrs.  I sleep better at night knowing I don't owe anybody money.

[Dave Spencer]

There are lots of variables. Here's some food for thought from a well regarded authority and a frequent contributor to this site.
YBYC
https://www.pbase.com/mainecruising/fuel_tankt_condensation

[Jon W]

The folks here with clean tanks are fortunate. If you've owned your boat for the majority of its' life, and practiced a good fuel regimen you may be fortunate too.

My boat was 28 years old when I bought her, and my fuel tank experience has been quite different. With the baffle in the center, I didn't see a way to inspect the inside of the fuel tank without access plates. I cut holes in the top of mine and installed two 8" access plates. The photo below is what I pulled out of my 1987 fuel tank earlier this year. (after 4 years, I did not see any contaminates in the Racor). After cleaning the tank, it unforunately began to leak so I replaced the whole tank with a more robust design which included relocation of the fuel fill hose, thru bolting the forward end of the tank to the mounting platform, and adding an aft hold down screw. I also changed the gate valve to a diesel compatable ball valve, added a second shut-off valve at the head door opening so I can reach it, and replaced the hoses to the Racor. See second photo.

[Breakin Away]

Wow, hard to believe that you had that much in your tank and didn't see anything come through the Racor.

I had seen MaineSail's blog on this topic before, but had forgotten how powerful it was. I might try draining my tank at layup this year and storing the fuel in jerry cans, then decanting/filtering back in next year. Previously I would run down my fuel through the season and top off before winter layup to avoid condensation. But that means my fuel is already 6 months old when I launch. So, just to try something different, I might leave the tank empty and top off with fresh fuel at the start of the season.

[Jon W]

About 1/16" thick hard layer across the entire bottom of the tank. Soaked it for days with a 1 to 1 mixture of Simple Green and water. Then used plastic scraper to peel it off the bottom. Whole process was just under 2 weeks. Then it leaked. 

[Breakin Away]

About 1/16" thick hard layer across the entire bottom of the tank. Soaked it for days with a 1 to 1 mixture of Simple Green and water. Then used plastic scraper to peel it off the bottom. Whole process was just under 2 weeks. Then it leaked. 

Reminds me of people who have old cars and switch from dino oil to synthetic. The synthetic oils dissolves all the gunk that was plugging the cracking seals, and ends up leaking.