Cleaning underfloor tank
Printed From: The Fishing Website
Category: General Forums
Forum Name: The Boat Shed
Forum Description: Discuss all things boating.
URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=27750
Printed Date: 26 Jun 2026 at 4:39am
Topic: Cleaning underfloor tank
Posted By: fluffy1
Subject: Cleaning underfloor tank
Date Posted: 11 Mar 2008 at 2:21pm
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Hi All,
Just wondering if anyone knows the best way to clean an underfloor fuel tank.The boats a tristram 691 with a 250litre tank.We have drained the tank and suspect salt water contamination,as the filters were fill of sea water.We believe the water was getting in through the filler as the seal was perished and it sits on the portofino which when its rough is contantly awash.We will take the tank out tommorrow.
Talking to a few people and they say to use meths.Talk to a few more people and they say don't.Is there a product on the market for this ? If not whats the procudure? Any advice would be great.Ps we are replacing the filler and moving it and the breather.
Cheers
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Replies:
Posted By: ohsif
Date Posted: 11 Mar 2008 at 2:35pm
| Meths and Isopropyl alcohol absorb water which is why they are often used to clean fuel tanks. They are also solvents. Not sure why you wouldn't use either. |
Posted By: Blue Legend
Date Posted: 11 Mar 2008 at 3:02pm
| If it was salt water, meths etc would absorb the water but may leave a salt residue on the bottom. I Can't see any reason you wouldn't use it either. |
Posted By: plastic
Date Posted: 11 Mar 2008 at 6:20pm
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If your taking the tank out cant you just flush it out with a bit of petrol. Slosh a litre aroung and tip out a few times. Meths does absorb water but If I remember right it only absorbs a small amount. Something like 1 litre will absorb 5 mls and as above what about the salt.
Cheers
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Posted By: fluffy1
Date Posted: 11 Mar 2008 at 6:49pm
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Cheers for the info guys but until I see the inside of the tank if I can.I cant be sure on the state of it.I guess it all depends on inspection and its condition.Draining the old gas didn't excactly leave us happy seeing the condition of it. |
Posted By: Quo vardis
Date Posted: 11 Mar 2008 at 7:38pm
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I had exactly the same problem after fuel cap wasnt screwed fully down onto its seat on a Haines Hunter 650. I used a small scavenger pump on the fuel line to suck out as much as i could then added some meths and small amount of petrol, and sucked out again, finally removed fuel filler line and dropped suction hose into back corner of tank, recovered about 2 L of water all up. Borrowed an endiscope and had a good look in the tank, no sign of any water or salt.
 Would help heaps if they fitted a drain to the bottom of the tank, as built there is no way to remove any water etc easily without removing the tank.
------------- If the conditions are marginal, you need a bigger boat |
Posted By: saltshaka
Date Posted: 12 Mar 2008 at 7:53am
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ive used meths to clean up my underfloor tank, up until i did that i was emptying my water seperator filter thingy, after every trip, but i was getting sick of doing that so i put a bottle of meths in about 20 l of petrol and end result is no more water in tank.
my theory on the salt supposedly left behind is this--- the reason salt water is bad is the fact that it doesnt burn and stays in your engine, hence the meths, and i would imagine that once the salt water and petrol have been mixed together by the meths, the salt ends up burning up with the petrol and out your exhaust.----- maybe? ------------- GET REEL! |
Posted By: ian
Date Posted: 12 Mar 2008 at 6:32pm
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my underfloor 200L tank (AMF) was full of all sorts of unpleasant crap when i got the boat causing lots of flow issues. Pulled it out, took it to washworld and rinsed it with teh engine cleaner/degreaser then high pressure water rinse a few times, then took it home, put my hotair paint stripper gun on low heat against the inlet with all other connections open for a while. tehn put 10L of petrol in sloshed around/inverted tank etc tehn tipped gas out inot a clean bowl and inspected, still dirt and water. filtered teh petrol with fine cloth, put it back in, repeated this till teh petrol coming out was clean. reinstalled tank, put 50L gas in, about 250ml of meths and went out, ran fine and has done ever since. I couldnt find anyone commercially to help nor any other useful info hence the possibly unusual approach! ------------- drink up stream of the herd |
Posted By: Rockhopper
Date Posted: 13 Mar 2008 at 9:07pm
Ethanol wholely disolves in water. There is a good bit of detail here http://www.oregon.gov/OSMB/news/E10.shtml - http://www.oregon.gov/OSMB/news/E10.shtml , remember its aimed at users of ethanol blend fuels but you can see by adding etanol to the mix it will absorb the water. I think that as the salt is already wholely disolved it wont seperate out from the ethanol. You can test this , mix some salt water in a glass of vodka and see what happens. Dont drink it.
Anothe item i have heard of is that chamois leather does not absorb fuels , therefore stuffing a shammy down the bottom of the tank will remove the water. ------------- Why does the answer to all government problems involve taking more of my money ? |