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Author Topic:   Water Fuel Separator on Evinrude 90-HP
FlyFishers2 posted 11-21-2006 05:07 PM ET (US)   Profile for FlyFishers2   Send Email to FlyFishers2  
Greetings. Two years ago my wife (she buys the boats in the family) bought a 1995 Montauk with a 90 HP, 1995 Ocean Pro V4 Evinrude Outboard on it. This was, apparently, one of the first of their fuel injection models. Although in beautiful condition, we are adding a few things getting ready for the month of May next Spring in the Keys chasing tarpon. She purchased a "Marine Water Separating Fuel Filter" because there is no water separator and we had one on another marine craft (150 HP Mercury) we used in Oregon for 10 years changing the canister every Fall.

She was asking a local boat shop (Tucson, AZ) about installation of the separator when they mentioned that we shouldn't use one if that particular motor did not already have one. They mentioned restricting the fuel flow and something about harming the injector system. So, we are wondering if this is reasonable information and would like to ask for your help on the question of whether an in-line separator can be harmful to certain motors. We will also ask Evinrude, but sometimes one gets a different slant on a question from users rather than makers/dealers.

Fred Rickson

Mambo Minnow posted 11-21-2006 08:44 PM ET (US)     Profile for Mambo Minnow    
Look under the cowl for a water separating filter. Mercury's OPTIMAX for example, has one under cowl and Merc recommends against adding an external one to the fuel line precisely because of fuel flow restriction problems.

We have a 1984 Evinrude VRO 90HP and successfully added a racor to it this summer due to 10 percent Ethanol concerns.

contender posted 11-21-2006 09:36 PM ET (US)     Profile for contender  Send Email to contender     
OMC makes a simple and cheap one,(its a spin on type) looks just like a oil filter and the replacement is about 8 dollars. Place it between your tank and engine. I do not think that this filter has an effect on their engines...good luck
jimh posted 11-22-2006 08:58 AM ET (US)     Profile for jimh  Send Email to jimh     
Give some thought to finding a better dealer for your OMC motor. Here is why:

I am just about certain that a 1995 Evinrude Ocean Pro 90-HP V4 is not a fuel-injected motor. If you take the cowling off and remove the air silencer I am just about certain you will find four carburetors on the motor. Your dealer should have known this and disabused you of the notion you had fuel injection on that motor.

Also, the motor very likely has the Oil Metering System (OMS, or often called by its earlier name, VRO). On Evinrude motors with the OMS there is a fuel line vacuum sensor which continually monitors the suction in the fuel line. If there is a restriction in the fuel flow which cause the fuel supply line suction to exceed a limit, an alarm will sound and a visual indication will appear on your SystemCheck gauge to inform you of the problem. This is a unique feature of the system; you won't find this on other motors.

The significance of this vacuum pressure monitoring is that you can safely add a water and fuel separating filter to the fuel system and be confident that it is not causing a restriction because, if it were to cause a restriction you'd get an alarm. I have just such a filter installed on my boat and I have an Evinrude motor with the OMS or VRO system. And so do thousands of other owners of Evinrude motors with VRO or OMS oil systems.

Finally, it occurs to me that perhaps you or your dealer are using the term "fuel injection" to refer to the OMS or VRO system. If that is the case, you two are probably the only two on the planet to use "fuel injection" in that sense, and you have confused the term with its proper use, referring to a method of inducing fuel into the cylinder via an injector as opposed to a carburetor. If your dealer is similarly misinformed, it is another reason to look for a new dealer.

The motor also very likely has a fuel filter located under the cowling. If there is any concern about the condition of this filter, just replace it. It is not an expensive item. In most cases when a fuel and water separating filter is located upstream of this engine filter, there will be very little debris in the engine filter.

For a fuel and water separating filter the RACOR unit is recommended. There is an excellent article in the REFERENCE section about these filters. See

Screen Test fuelFilterTest-TrailerBoatsMag.pdf

to learn why the RACOR is your best choice.

FlyFishers2 posted 11-22-2006 11:18 AM ET (US)     Profile for FlyFishers2  Send Email to FlyFishers2     
I thank you folks for your time and thoughtful replies. I have been enlightened, and appreciate your patience.

I knew that there were 4 carburetors under the cowling, which was why I was confused by our local marine tech discussing fuel injection...thought I had missed something. Your suggestion to change marines is well taken.

Until the next question, Melinda

jimh posted 11-22-2006 01:55 PM ET (US)     Profile for jimh  Send Email to jimh     
It is common for an engine which has fuel-injection to have its own fuel and water separating filter under the cowling, but on this OMC carburetor engine I do not think you will find one. The fuel filter under your cowling is just a small screen filter designed to remove solid matter in the fuel supply.

Engines with fuel injection usually have a filter system which will separate water and also remove any vapor from the fuel supply. It is important to the operation of a fuel injector that it not be supplied with air or water mixed in the fuel, and the engine designers go to lengths to provide that with filters under the cowling.

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