Fuel/water separator

[YoCon]

Why do people use them and, are they needed if you are already running an in line fuel filter?

[Raceman]

See the "Do I need this?" thread.

The answer to the why people need them is that you don't know what you're getting along with the gas when you buy it, and there can be condensation issues as well, depending on a number of factors. An inline filter won't do anything to remove water.

[novalves]

WATER = BAD
FUEL = GOOD

SEPERATION MEANS THAT EVIL MR WATER CAN NO LONGER INTERMINGLE WITH YOUR PRESIOUC HYDROCARBONS.THEREFORE IT WILL BE KEPT FROM REACHING YOUR ENGINE.

At best water will cause your motor to temporarily stop!!

At worst water will cause your motor to permanently stop!!


In a multi cylinder engine with multipal carburetors water usually enters one float bowl first. Because water is heavier than fuel it will not pass thru the carburetor. This Prevents fuel (at least 50% of your pistons coolant) and oil from reaching your pistons rods crank ect.

As the motor seems only a little down on power the other cylinders continue to fire while draging the starved ones along without any fuel or lube they usually fail causing catastrophic dammage to the engines internals.

A lot of water usually is less harmful beacause its presence is obvious.

Small amounts of water can sometimes go unnoticed causing greater dammage.

Personaly I install water seperators on all boats that I rigg and every time I am involved with fuel system repairs.

Their large volume (trapping lots of junk before limiting flow) is also handy in situations where the tank or lines are known to have had a corrosion or rust problem.

[Techno]

In your example with carbs how does this relate to EFI where all the injectors are pushing some water mash into the cylinders?

Is it just a lean condition or something else?

[novalves]

Water takes the place of fuel and with only the total volume of what ever is in the lines being metered sounds like lean to me

[W. Tripp]

Water weighs around 8 pounds per gallon. Fuel and oil weighs in around 6.25 pounds per gallon. If you get a large amount of water in your tank, it will try to seperate and sink to the bottom of the tank where the fuel pick up is located. If you get a small amount of water or condensation in the tank, it will generally stay in the fuel, and a seperator can catch it. If you are running synthetic oil, the oil can blend with the water and in small amounts, will cause no problems - even at over 11,000 rpm (don't ask how I know).

If enough water gets into the fuel/oil the injectors will spray the mix into the crankcase, and the main and rod roller bearings will not get the protection they need - to say nothing about the bores.

For a lake boat, keep the seperator, pull it off and drain it often - if it gets full of water it can't do its job any more.

I hope this helps.