• Mobile App For Android Now Online!

    Download it here. The app is searchable in the Google Play Store under Sailboat Owners.

    Sorry iPhone/iPad users, we are still waiting on Apple. :(

    Click the X in the upper right corner to make this go away

How do I clean my fuel tank?? 1979 Newport 30


Sep 14, 2012
Newport 30 mkll Oro Bay, Anderson Island, WA
Greetings Skippers,
After replacing every part of my fuel delivery system, I'm still not able to start my M25 Universal. I have air, I have compression(400+ on each cylinder, and I have been getting fuel. The last thing to check was the condition of my fuel tank. I did that today. With ALL 30 gallons drained, I shined my light down in there and the attached picture is the result. After pouring a little biobore directly on it, the growth ran to the lowest part of the tank. However, my opening is only about 3" wide(circular), leaving me not many options for cleaning the tank.

My thinking is that I will fill my garden spray pump with some clean diesel and a heavy dose of biobore and use the wand to reach the back parts of the tank. Then I plan to use a disposable wet/dry vac and suck everything out, as the lowest point is below my small access hole.

Thoughts?? Thanks in advance for any advice/suggestions.


Last edited:
Sep 4, 2007
Hunter 33.5 Elbow, Saskatchwen, Can.
I don't think I would use a wet/dry vac to suck fuel out. I have a vacuum pump that I use for changing the oil and would use that to clean out the tank. I like your idea of using the spray pump to get into the corners and back parts.
Hope this helps.
Jan 19, 2010
Catalina 34 Casco Bay
The absolute best way to clean a tank is with a polishing system. Google marine fuel polishing in your area. You should be able to locate a mobile system. Basically they will suck out your fuel, filter it and return it thru a pressurized line that has for the lack of a better term a Bresnan distributor on the end. This agitates the sediment, puts into suspension for the filters and the cycle repeats. Works very well..


Mar 16, 2010
Beneteau 411 Oceanis Annapolis
Doesn’t look too bad but you need better access, AND forget about that shop vac idea. Boom. Check to see if you have a baffled tank, then get the right number of access ports:

If you are cutting on a diesel tank, inert it first. Dry ice works well and leaves no residue. It ensures you don’t have oxygen in the tank necessary to make the Boom. Once you have good access you can simply wipe the critters and sediment out. Inspect the side walls, stuff clings. Wear gloves, that BioBor you are tossing about is a pesticide.
Apr 8, 2010
Ericson Yachts Olson 34 Portland OR
What Gunni said. Further, the picture makes the "dirt" look like pitting in the aluminum. (Over time, water droplets in the fuel can corrode the tank.)
By the time you get done with building and installing a polishing system or paying someone to do the work, You will find that you are financially much of the way toward a new tank.
That new tank will also have a clean-out port(s).
I replaced our original diesel tank with a new and larger one. Heavier wall thickness nowadays, as well.
We now have two clean out ports and an electric fuel level gauge. (!)

This was part of a wider-ranging project to replace all of the original fuel system hoses, and even the deck fill. That was a decade ago... no more seeps or odors. Even if you are not keeping this boat for another XX years, you still need to have this stuff work reliably so you can enjoy that boat.