Condensate in fuel

Beefer

Lieutenant Commander
Joined
Aug 4, 2008
Messages
1,737
I put in a new f/w separator about 3 weeks ago, drained the old fuel, tested (with Kolor Kut) for water in the old fuel before removing, and am using only non-ethanol fuel. The other day, I was drained my fws, and there was water. Hmm. Today, when I opened the fuel cap, I noticed condensation on the inside of the cap. I figure that condensation is my culprit. How do I address this? It isn't coming from the vent, as the vent was corroded and now vents into the cockpit (I know, I know), so it isn't exposed to seawater or rainwater. When we have heavy rain, I noticed that some gets below the fuel tank access hatch, so I changed the sending unit gasket as a precaution. Any ideas on preventing/limiting condensation?
 

Beefer

Lieutenant Commander
Joined
Aug 4, 2008
Messages
1,737
Re: Condensate in fuel

I don't know of any standing water in the boat. There is a little in the bilge, but I can't get to it, and neither can the pump. The boat is kept in the water though.
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
Re: Condensate in fuel

If you keep your tank full there will be less air in the tank from which the water can condense. Condensation occurs with temperature change. And it there is a lot of air in the tank there is more opportunity for fresh damp air to get in there through the vent when the temperature changes causing the fuel & air to expand & contract.
 

oldjeep

Admiral
Joined
May 17, 2010
Messages
6,455
Re: Condensate in fuel

If you havn't seen issues in the past it is more likely that the last time you filled up you got some gas with your water and the condensation on the gas cap is from the water that was pumped into the tank.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: Condensate in fuel

Condensation is not caused by the fuel tank vent being on the exterior ogf the hull. The dampness that causes condensation is in the cockpit as well, and actually the cockpit could be damper than the outside air, it it has a cover.

Empty the FWS a few times to rid yourself of the water. A better choice is to pull the gauge sender and pump out the very bottom of the tank. I think you will find significant water. Siphon the fuel into a clear container. If you are using straight gasoline, add a bit of 2 cycle oil to color the gas. You can then see the water, and save the gas for reuse.
 

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,688
Re: Condensate in fuel

Never heard of adding two cycle oil to help see water but I understand the concept, water in the fuel is easily seen without adding anything.
take a jar of gas and put a shot of water in it you'll see, shake it up swirl it whatever the water and fuel will always seperate to the bottom.
 
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