Where is the fuel water separator located?
The fuel filter/water separator is located under the seat on the left side of the vehicle, between the engine and fuel tank.
How to change a fuel-water separator in a Yamaha outboard motor.
The buildup of water stops the fuel filter from separating out the bad particles in your fuel. These particles will build up in your fuel system and engine causing damage to those components. The best way to fix this issue is to make sure you replace this part as needed.
How A FUEL WATER Separator Works! - YouTube
How to Change Fuel Water Separator on your boat's fuel line - YouTube
Like other filters and fluids, the fuel water separators in your boat should be changes out each spring. Not only could it be full of gunk from last season, but could have collected more dust if not properly stored over the winter months.
How To Replace Turbo Diesel Fuel Filter & Water Separator 2017 ...
If you use gas w/ ethanol, you are bound to get some water in your fuel. Don't know what type of engine you have but Yamaha recommends every 50 hours. I agree with Bunger79 until you consistantly have a clean filter, then I would go to 100 hours.
Should You Pre Fill A Boat Fuel Filter or Water Separator? Yes, pre-filling a boat's fuel filter or water separator is a great habit. You won't cause any harm to the engine and it will make your engines fuel lift pumps job much easier. This eliminates the introduction of a large amount of air into the fuel system.
Diesel fuel can easily become contaminated by water because diesel fuel absorbs water more than gasoline does. For this reason, many diesel vehicles feature a gadget called a water separator that collects water from the fuel. It's usually located on or near the fuel filter.
How often should you drain your fuel water separator?
If you use gas w/ ethanol, you are bound to get some water in your fuel. Don't know what type of engine you have but Yamaha recommends every 50 hours. I agree with Bunger79 until you consistantly have a clean filter, then I would go to 100 hours.
The principle behind this filtration system is surprisingly simple; the top of the filter consists of a paper element and the bottom of the filter is a holding tank or bowl. Since water is heavier than petrol, water sinks to the bottom of the filter where it stays until it is emptied.

Fuel Water Separator on Cat® D Series Skid Steer Loaders - YouTube