So I've been having some issues with intermittent bogging when cruising ('90 Merc. 4.3L). I'm pretty sure that it's an issue with water in the fuel. I've installed a fuel/water separator filter and am now going to siphon the remaining gas out of the fuel tank. I read that you can let the gas & water separate and then reuse the gas. My question is how long do you need to let the gas to sit to make sure that the gas & water have completely separated out? Does it take place pretty much instantly or do I need to let it sit for a while? If I need to let it sit, how long would you recommend?