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Nasty black sediment in fuel filter

Tikitech

Member
This was off a rental boat we were servicing, it's like a black residue from fuel hose breakdown maybe? Just wondering if anyone has seen something similar. It was in water separator filter. <img src="http://www.marineengine.com/boat-forum/attachment.php?attachmentid=22986&stc=1" attachmentid="22986" alt="" id="vbattach_22986" class="previewthumb">
 
Probably from the tank. Organisms grow in the bottom of the tank below the fuel if there is any water. The black is their waste. It's acidic and will eventually eat holes in metal tanks. The solution is a fuel conditioner with a biocide. Probably a triple dose to kill the organisms and the black will slowly disappear and be found in the filter. It may require regular treatments to fully kill the organisms. The black usually doesn't plug a filter, just looks bad.
I use a fuel conditioner every time I fuel and never have fuel problems.
 
Appreciate the response this boat is a rental at a resort on a local lake. They had sketchy management since opening and a new guy has taken over. Ill pass the info along to him so they can deal with it appropriately with their staff and fuel supplier. It hadn't gotten into the secondary filter so all should be good. It's something I'd never seen until now so I learned a little. Thanks again!
 
About every two years with my boat on either my lift, or on my trailer, I will jack up the bow and tilt the boat to one side. Let it sit that way for several hours - or days if you have the time. Then remove the hatch for the fuel level sender (If the hatch for the fuel pick-up is more convenient, use that) and snake a small hose to the lowest corner of the tank, and pump out several gallons of whatever is there using an aftermarket 12 volt fuel pump. (A hand pump will work as long as it is rated for distillates.) I'll usually get anywhere from a quart to a gallon of water, gunk, and red/black grime.

As Lepke stated, bacteria will grow in the water. The water gets there because the tank is not sealed so you can get considerable condensation from the surrounding air. Plus, some marinas never drain their storage tanks, and don't have effective filters on their dispensing hoses, so you can get water in the fuel from there, also.

BTW - it's always a good idea to occasionally pull the fuel pickup tube out of the tank and give it a good inspection. Some have a screen on the end which can get clogged up. Also, most have an anti-siphon valve at the top where it screws into the tank. Make sure it is working. If not, replace it. In older boats, the pickup tube was plastic, which can be compromised my ethanol fuel. Make sure yours is aluminum.
 
More excellent information, thank you. I had a conversation today with the new manager of the resort. With this virus crap going on they have been shutdown so this boat may be on our lot for awhile. It doesn't sound like they had a very good maintenance program for their fleet of rental boats in the past and we will be putting together some recommendations for them to consider. This was the first of a dozen boats they had planned on bringing in as they gear up for the season. It's a pretty good client to have for our shop down the road. He is still taking stock of all the vandalism done to their boats while in storage over the winter so we may pick up that end of it too since we have secure storage unlike many places around here. Not having to replace batteries and repairing cut fuel lines every year would make up for the difference in cost lol. I did pump out about 1/2 gallon of gunk out of the tank, after we pulled the filter and saw the black stuff I couldn't walk away without making sure there wasn't more in the tank. Thanks for the info fellas like I said before I learned something here and I appreciate passing along the knowledge. Hopefully I can occasionally do the same.
 
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