Fuel Water Separator Placement behind Fuel pump

[JC766]

Hi guys, having owned several mercruisers I know our F/W Separator was always before the inline pump. My new (used) boat has the pump in the tank and no F/W separator. I have read a few posts that indicate the preferred method is having the F/W Sep in front of the pump. What I can't really find is will it still work after the pump since I will have no other choice because the pump is in the tank. In theory an F/W Sep is gravity based. But is there any proof that it still works when the gas lines are under high pressure?
I have read several posts of people adding them to boats with in tank fuel pumps after the pump. But is the conesus that they won't work and it is just a waste of money? I'm thinking at the very least it may provide some filtration to my gas lines even if it fails to trap the water. Thoughts?

 

[Bt Doctur]

I know of no manufacturer that has a pump in the tank

 

[H20Rat]

Hi guys, having owned several mercruisers I know our F/W Separator was always before the inline pump. My new (used) boat has the pump in the tank and no F/W separator. I have read a few posts that indicate the preferred method is having the F/W Sep in front of the pump. What I can't really find is will it still work after the pump since I will have no other choice because the pump is in the tank. In theory an F/W Sep is gravity based. But is there any proof that it still works when the gas lines are under high pressure?
I have read several posts of people adding them to boats with in tank fuel pumps after the pump. But is the conesus that they won't work and it is just a waste of money? I'm thinking at the very least it may provide some filtration to my gas lines even if it fails to trap the water. Thoughts?

Before or after makes zero difference. The internals of the fuel/water separator do not know or care about pressure, the system is sealed and not vented to atmospheric pressure at any point. Fuel flow is also exactly the same before or after the pump, it is a certain number of gph regardless of where you place it.

 

[Bondo]

Before or after makes zero difference. The internals of the fuel/water separator do not know or care about pressure, the system is sealed and not vented to atmospheric pressure at any point. Fuel flow is also exactly the same before or after the pump, it is a certain number of gph regardless of where you place it.

Ayuh,.... That may well be true,.... But,..... Why would ya pump crud through the pump, to get to the filter,.....

The filter goes 'tween the tank, 'n pump to save the pump,.....

I'm with BD, there ain't no boats with the pump in the tank,....

 

[dingbat]

Before or after makes zero difference. The internals of the fuel/water separator do not know or care about pressure, the system is sealed and not vented to atmospheric pressure at any point. Fuel flow is also exactly the same before or after the pump, it is a certain number of gph regardless of where you place it.

You would be correct for a fuel filter, but separators are gravity systems designed to work on the suction side of a pump. Pressurizing the housing will push the water right thru the filter.

http://realitycheck.me/docs/Racor spin-on fuel filter separator.pdf

 

[JC766]

Some boats have pumps in the tank. They are the same pumps that are used in car gas tanks. In fact I have two. While there may not be a mercruiser designed that way, yamaha and seadoo boats are. Thank you for the article!