Pontoon Boat & Deck Boat Forum

I recently purchased my first Fuel Injected outboard ,(115 Mercury) all my other boats have always been carb engines.
I know from experience with diesel pickup trucks that water in fuel can cause many dollars worth of damage to electronic diesel engines

Would it be wise to add a water seperator on my engine and if so how is it done.I'm assuming my fuel pump is in the tank on my boat so fuel pressure would be a lot higher on the line and simply splicing the seperator in line wouldn't work

Kytim wrote: ↑

Sun Feb 23, 2020 6:50 pm

I recently purchased my first Fuel Injected outboard ,(115 Mercury) all my other boats have always been carb engines.
I know from experience with diesel pickup trucks that water in fuel can cause many dollars worth of damage to electronic diesel engines

Would it be wise to add a water seperator on my engine and if so how is it done.I'm assuming my fuel pump is in the tank on my boat so fuel pressure would be a lot higher on the line and simply splicing the seperator in line wouldn't work

Fuel pump is on the engine. It should be as simple as splicing it in and mounting it upright. I like the Racor fuel water separator with the clear bowl. It lets you see if there is any water in the bottom of it and drain it out if needed.

I don't know how to tell you how to add it to your rig, but I think it's a good idea to add the water separator...

FWIW, I wanted my dealer to add one to my merc 200 and they said no need to??? Said that my engine had a fuel water separator on it?? mine is a 2018

Sounds crazy to me but......so far no issues.

My old Yamaha 115 4-stroke is injected. It has a clear bowl factory mounted fuel filter/water separator under the engine cowling AND a large inline unit - same size and shape as an automotive oil filter on a V8. The large size provides more surface area to keep the pressure drop to a minimum. I have never seen water or fouling in the clear factory filter. I am a big believer in having an additional filter/separator in series. Mine is mounted at the stern where my 12-gallon portable tanks are. The motor mounted fuel pump easily sucks gas from the tanks, through the filters. Keep in mind that you are only talking about 10-11 gallons per HOUR running wide open with 115 HP. So 10 gallons/60 minutes = 0.17 gallons per minute. So about 22 ounces per minute - you could run a skinny siphon hose faster than that

Buy a screw-on filter kit that is rated for 10 microns or better in order to remove even the smallest particulates, along with the water separator action.

Marc

I'd take down the model number, VIN, build date, etc and send a message to Mercury. Chances are it has a water separator under the cowl already like Honda and others. I believe some outboards are built with one factory installed at the engine and some are built to have one added externally. What you can run into if it's got one already and not built for an add on is the add on becomes a restriction. Fuel pumps are better at pushing than pulling and putting anything inline before the pump can lead to issues if not designed for it.
https://www.youtube.com/watch?v=YniVqyJtIrA

Also FWIW I go ahead and run Stabil 360 in every tank of gas even though I run 90 octane E0....it only adds about 7 cents a gallon.
My Honda 90 had a serviceable separator under the cowl, my Yamaha F200 (on a G3 by Yamaha boat) has the big external one.