Water fuel separator Mercury 4 stroke

[j791]

For those with a Mercury 4 stroke, did your boat come with a water/fuel separator filter? I know there is a fuel filter on the motor, but I noticed Mercury sells one on their website so I called them. Sure enough, they sell a kit for my 2018 150 four stroke. Just curious how many people have one installed.

[Joe4d]

Ive got same question , been using them on work boats ever since the ethanol thing Had a few folks say they arnt needed but no whys or links to any thing from mercury. Cant really see the negative to these unless some how the bit of extra load to the fuel pump. But really I think water in fuel is worse.

[j791]

The Mercury customer service guy said you have to make sure your motor is within the specs for one...something about low pressure/volume? He looked up my motor to see if it qualified and quickly verified a kit was available for my model.

[Joe4d]

One of those Spin on 20 Micron external units with he drain bowl on bottom is gonna move alot more fuel than those smaller engine mounted ones. Dont see it being an issue. Those units have 4 ports, 2 in 2 out. Couple T's and you could run a bypass. Or put a $6 vacuum gauge on the discharge side.
I mean not that complicated,, Sitting right now with 4 generators a main engine (diesel) and an outboard. All have racors primary water seperator and then a smaller micron.. In fact out side of personal boats I have never seen ANY marine application engine that didnt have one.

[Lou r Pitcher]

A couple points.... an external water sep itself does not significantly increase the vacuum. A fuel filter if included with the water sep though will increase the vacuum. Note that a fuel filter, even a 10micron one cannot itself filter a water molecule.

The need for a fuel/water sep is reduced for those boaters always running ethanol blended fuels. The ethanol in E-10 will bond with the small amounts of water present in our fuels and will safely pass through the filter, through the water sep, through an engine and out the exhaust (along with all the vast quantities of water vapors being taken in by the air intake).

It's the Pure Gas folks that have little or no way of ridding their tanks of accumulated water until one day it reaches the tank's pickup. And without a water sep, the water molecules will pass directly into the engine possibly shutting it down and remaining on the engine's internal metals and oxidizing their surfaces.

[mikesxpress]

Mercury states, and has always stated, the filter they supply on the engine is all that's required. While there maybe some commercial installations that might require and additional onboard filter our fishing rigs don't. I have a new 250 4.6L PRO XS and will use the engine mounted filter as I did with the previous Opti.

[Tromanoski]

My Yamaha has an external fuel filter as well as one on the engine. I never had an external one on the Evinrude that I ran for 23 years prior to buying the Yamaha in 2012. I have change the external filter 3 times and the internal filter once. Never have seen any water in either of them. I always have ran ethanol gas in both engines and never have had a problem. I do without fail add the prescribed amount of ring free and stabil when I fuel up. I also always buy from high volume dealers because I know they will more than likely maintain their tank/pump water monitoring/filter systems. I agree with Mikesexpress. If the engine manufacture tells you its not necessary with their motors, I would not put one on. I would not give them an excuse to possibly void a warranty by installing something they said is not needed.

[j791]

Here is the water/fuel separator on the Mercury site.

https://www.mercurymarine.com/en/us/...are/fuel-care/

[mikesxpress]

Yes they do sell an after market filter but you don't need it. Mostly used for commercial applications where the boat stays in the water and when it is used you remove the one on the engine.