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This note is to relate my experience cleaning a badly gunked up fuel tank in place.
I use my Pearson 35 mostly for day sailing which only requires about 1/2 gallon of fuel in and out of port. As a result fuel can remain in the tank for well over a year. I use stabalizer and had not had problems or so I thought. What I didn't realize is that a thick tarry layer was building up in the bottom of the tank. I noticed it only when my fuel filter plugged and subsequently when I probed the tank with a wooden rod. It had a consistency like tar that was very evident on the stick.
To remove it, I first pumped the gasoline from the tank. I pumped it out through the filler pipe in the cockpit with an inexpensive automotive electric fuel pump in a length of 3/8th fuel line that I purchased at an auto supply store. I wired a cigarette lighter 12 volt male plug on the pump wire and ran it from the boat 12 volt supply. All of the gasoline handling was in the cockpit which I considered safe. Next, I poured two gallons of laquer thinner in the tank and let it slosh around for about two weeks. That disolved the gunk. I pumped that out. Then I added a couple of gallons of gasoline and a can of fuel injector additive and let that slosh around a couple of days and pumped it out. I repeated this a second time and as best I can determine, that cleaned out the gunk. I put a clear plastic fuel filter in the line each time I pumped the tank. I found I couldn't use the filter when I pumped the lacquer thinner as the filter quickly plugged. I was able to filter the first gasoline flush but still saw some pretty ugly black stuff coming through. I did not see anymore of it with the third flush. Probing the tank with the wooden rod also shows no more evidence of the black tar. These flushes need to be disposed of -- the definitely cannot be used used in a lawmower engine and in fact, can pretty well mess up a gas can. (I found cheap 5 gallon cans at Sam's, btw.) Only after the second flush did I pull gasoline from the tank through my on-board electric fuel pump system.
I relate this in case my experience is useful for anyone else. I'm not sure if this is an approved method or anything Don would approve, but it seemed to work for the thick tar like organic material in my tank and was much easier than removing the tank. I didn't have any solid material, like rust, dirt, or sand and suspect what I did wouldn't work for that sort of contamination. Depending on the organic material in the tank, it could take more than one lacquer thinner flush I suppose. One can determine that by probing the tank after the first batch has sloshed around and also by observing what you pump out.
Based on what I found in the tank, my plan from now on is to pump the tank out each fall, use that gas in the lawn mower, and add about five gallons of fresh gas with stabalizer to the boat tank. I may repeat that in the spring as it is easy to do. I have never seen any evidence of water (condensation) in the fuel tank, perhaps due to the ethanol in gasoline today. So I don't see a reason to keep the tank full.
Bob (1975 Pearson 35)
I use my Pearson 35 mostly for day sailing which only requires about 1/2 gallon of fuel in and out of port. As a result fuel can remain in the tank for well over a year. I use stabalizer and had not had problems or so I thought. What I didn't realize is that a thick tarry layer was building up in the bottom of the tank. I noticed it only when my fuel filter plugged and subsequently when I probed the tank with a wooden rod. It had a consistency like tar that was very evident on the stick.
To remove it, I first pumped the gasoline from the tank. I pumped it out through the filler pipe in the cockpit with an inexpensive automotive electric fuel pump in a length of 3/8th fuel line that I purchased at an auto supply store. I wired a cigarette lighter 12 volt male plug on the pump wire and ran it from the boat 12 volt supply. All of the gasoline handling was in the cockpit which I considered safe. Next, I poured two gallons of laquer thinner in the tank and let it slosh around for about two weeks. That disolved the gunk. I pumped that out. Then I added a couple of gallons of gasoline and a can of fuel injector additive and let that slosh around a couple of days and pumped it out. I repeated this a second time and as best I can determine, that cleaned out the gunk. I put a clear plastic fuel filter in the line each time I pumped the tank. I found I couldn't use the filter when I pumped the lacquer thinner as the filter quickly plugged. I was able to filter the first gasoline flush but still saw some pretty ugly black stuff coming through. I did not see anymore of it with the third flush. Probing the tank with the wooden rod also shows no more evidence of the black tar. These flushes need to be disposed of -- the definitely cannot be used used in a lawmower engine and in fact, can pretty well mess up a gas can. (I found cheap 5 gallon cans at Sam's, btw.) Only after the second flush did I pull gasoline from the tank through my on-board electric fuel pump system.
I relate this in case my experience is useful for anyone else. I'm not sure if this is an approved method or anything Don would approve, but it seemed to work for the thick tar like organic material in my tank and was much easier than removing the tank. I didn't have any solid material, like rust, dirt, or sand and suspect what I did wouldn't work for that sort of contamination. Depending on the organic material in the tank, it could take more than one lacquer thinner flush I suppose. One can determine that by probing the tank after the first batch has sloshed around and also by observing what you pump out.
Based on what I found in the tank, my plan from now on is to pump the tank out each fall, use that gas in the lawn mower, and add about five gallons of fresh gas with stabalizer to the boat tank. I may repeat that in the spring as it is easy to do. I have never seen any evidence of water (condensation) in the fuel tank, perhaps due to the ethanol in gasoline today. So I don't see a reason to keep the tank full.
Bob (1975 Pearson 35)
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