Cleaning fuel tank on board.

Alansails · Dec 3, 2016

When we bought our boat we had to have the fuel polished so no we did not pull the tank, and we hired that done and glad we did.
Our tech editor, Jesse, may have insight/ or may have done that to their boat.

valcour · Dec 3, 2016

It will be difficult to do on board. I had to pull my tank to repair a leak, and determined that the baffle is longitudinal right in the middle. I think the best you can do is suck it out with a copper tube wand in the area close to the hole. This will at least get rid of the water and loose stuff if you can induce some heel to starboard. If you use the fuel pump to drain the tank, the fuel will be cleaned by the racor as it is drained. Once you drain the fuel tank and the hot water heater (based on your hull number likely a 6 gallon tank), it is only a couple hour job to pull them both out (two hold down screws and four hoses on the heater and two hold down bolts and four hoses plus sender wires to the tank). I used a rag soaked in boiling water on the supply, fuel, and vent hoses for about 5 minutes and they came off quite easily. Onshore you can pressure wash the interior. I took the opportunity to do a good flush of the water heater (quite a lot of crap in there after 13 years), touch up paint some pitted spots, and install a temperature mixing valve on the heater when I put it back in.

Ralph Johnstone · Dec 3, 2016

Clydo said:
Using digital camera discovered little bit of crud on bottom of my
tank.

Maybe looking for a problem where none exists. Your primary filter is more than capable of handling what you're seeing.

I use this access to pull out (using a Pela oil extractor) any small amount of water/crud which may accumulate at the lowest point in the tank.

centerline · Dec 3, 2016

Clydo said:
Anyone tried to clean tank without removing by going through fuel sending
unit hole? Using digital camera discovered little bit of crud on bottom of my
tank.
Clyde

its done quite often... but you must have patience so that you move slow and careful to avoid any fuel spillage, as it will smell up the boat for awhile.

it can be done with the fuel still in the tank as long as its not a full tank of fuel that will splash out the hole while the boat rocks around... or it can be done with the fuel level low...
personally, I would first use seafoam or a product similar to it to dissolve any gum or varnish build up within the tank.... a few hours in advance is all that is needed for the seafoam to dissolve any gum/varnish left by fuels.
then, use an oil change vacuum pump to suck everything out of the low spot of the tank.... the system will then be clean and without the debris. (there are several brands of vacuum pumps on the market to choose from)
the vacuum pump will allow you suck up the dirt and debris (and some fuel) from the bottom of the tank in the same manner that a vacuum cleaner sucks dirt off the floor....
OR, to help see whats actually in the bottom of the tank, you can pump out all the fuel, leaving a couple of inches in the tank, then use the vacuum pump to evacuate all the debris and remaining fuel.....

I have always found the most difficult part of the task is getting the fuel sender hole sealed up 100% on the first try....even with a new gasket this can sometimes be challenging on a boat fuel tank.
to insure a good seal on the first try is best accomplished by using a product called hylomar on the gasket... this products works as a gasket dressing and thread sealant for gas or diesel....
another sealant for gasket dressing or thread sealant is block... it is harder to find but is far above and superior to any other sealant of its type, as none of the common dressings and thread sealers are meant to be used with fuels and will usually degrade away..

KD3PC · Dec 4, 2016

Clydo said:
It looks like pretty big project to pull fuel tank from boat and clean it on shore.
Anyone tried to clean tank without removing by going through fuel sending
unit hole? Using digital camera discovered little bit of crud on bottom of my
tank.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

IF it is just a "little bit of crud" then the methods described may work, assuming you can get to the "crud" with some means of removing it. Thinking that you are going to do much to a multi-gallon, baffled (almost all are) fuel tank, using a 1/2" suction hose is just flawed from the get go - not going to happen.

IF there is tar and sediment and left over bio material (all of which will occur in diesel fuel tanks) - then the only way is to drain and remove the tank, gain access to the entire tank area and steam/solvent clean the tank.

Even fuel polishing is a misnomer, and may do nothing more than your current filter set up will do.

Charles Erwin · Dec 4, 2016

Here is a possible solution. The tank was quite long located immediately beneath the motor in the keel so removal was not convenient. Chemical/enzyme treatments were quite ineffective.

I made up two plates/gaskets and installed one in each end of the tank. These are like Ralph's plate only the hole in the tank is 4 inches diameter, the backside is reinforced, and I used studs for fasteners.

Such a plate permits access for a long handle brush. In this case the tank surfaces were also blasted repeatedly with a small Ryobi pressure washer. Spray/brush the surfaces, vacuum the water out, and repeat until the water comes out clear. These repetitions used about 3 gallons of water each pass.

Similar plates can be purchased from Seabuilt.

Charles

thinwater · Dec 4, 2016

This is done all the time in industry.

Pressure washer with a variety of angled tips, pumping out the wash water at the same time. Not that hard if you get the right tools lined up. Use the power washer in short bursts to minimize wastewater generation.

Ralph Johnstone · Dec 4, 2016

Clydo said:
Bit rough weather. Thought crud broke loose?

Any chance you have a filter cloth over the pickup tube in your fuel tank ? Can't speak from experience but many on this forum have said that they were plagued with a fuel starvation problem due to the small area of the filter on the tip of the tube. The primary and secondary filters have much larger filtration surface areas and are more forgiving as far as loss of fuel supply goes.

centerline · Dec 4, 2016

KD3PC said:
using a 1/2" suction hose is just flawed from the get go - not going to happen.

IF there is tar and sediment and left over bio material (all of which will occur in diesel fuel tanks) - then the only way is to drain and remove the tank, gain access to the entire tank area and steam/solvent clean the tank.

Even fuel polishing is a misnomer, and may do nothing more than your current filter set up will do.

1/4" hose is adequate for the task UNLESS you have an extremely rusty and flaking tank, or, someone you have pissed off has put rocks or marbles in your tank....its only a 3/8 line that sucks the debris into the boats fuel filters, and there are always screens (but NOT always proper filters) in the equipment that pumped the fuel to begin with, if only to protect THEIR pumps from damage. the debris in tanks is almost always in the form of sand/dust particles.
as for the tar, a proper additive will dissolve it so it can be removed/passed with the fuel, and the sediments can be sucked out....

I agree that a lot of the commercial fuel polishing companies may NOT clean the tank as fully as is possible if the one running the equipment would take the proper care, but ANYONE with the skills necessary to work on their boat can clean their own fuel tank. without removing the tank from the boat.

if one were to need their fuel tank any cleaner than the having the dissolvable and loose debris removed from it, then a steam cleaner would be necessary, which is different than a hot pressure washer, to sweat the walls down without an unnecessary amount of water being produced... but it STILL has to be sucked out.... unless the tank is out of the boat and it turned upside down while the cleaning process is taking place....

KZW · Dec 8, 2016

So, for the OEM fuel tank on the C-310, where is the lowest point in the tank?

mm2347 · Dec 8, 2016

Mr. Erwin is right. Corners, baffels, and bad angles make cleaning crud difficult at best. There are kits made to install in your tank to open it up so you can get at the crap and clean it out. Most of the time you'll not have to remove the tank but you will have to open it up (inspection port type kits) to scrape and glob the goo from its nooks and cranines of the tank.

mm2347 · Dec 8, 2016

Need to add. Sometimes its not just dirty fuel. You can clean your fuel but Its the crud that seems to grow in the tank and then attaches to the tank bottom and walls. It hangs on tightly until the boat is shaken very hard by seas most often avoided by us. Then your in trouble. Probably the only sure way to get this crap out is to be able to get at it. Install opening kits.

valcour · Dec 9, 2016

KWZ, If on a level heel, the lowest point is directly on center-line, forward. The tank is tapered, with the longest side to port.

KZW · Dec 9, 2016

Thanks!

Witzend · Dec 14, 2016

Beware...The low corner sits in a recessed area of the fiberglass, if any water gets in it will corrode from the outside. When reinstalling my tank after it failed I placed a small spacer under it to help keep it up and dry. My swim ladder attachment points were leaking and caused water to sit in this area. Had it patched and cleaned out. I remove all the fuel every year from the level transducer access, burn the excess in my home oil heater. Fresh fuel every spring.

Cleaning fuel tank on board.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

Attachments

.

.