Fuel Filter / Water Separator - To Install or Not?

[Zteven]

Here's the question: Would running a water separator after the primer bulb and an inline filter in the factory location ('90 150HP Black Max) put me at risk of a lean condition at WOT?

Between reading the various forums I'm stumped:

High Performance (S&F.com) guys say no to the water separator, citing that it can restrict fuel flow and cause a lean condition at WOT and burn out a powerhead.

The fishing guys say yes to the water separator as well as another inline filter to protect the engine against water / debris in the fuel.

By no means do I have a high performance boat (16' Sidewinder), but I do run the engine up to 5800RPM (150 Black Max) from time to time for a good speed run. I've had two older engines burn out on me and I've finally spent a few $'s to buy a nice rebuilt engine and I want to do everything I can to ensure longevity.

 

[Sea Rider]

Re: Fuel Filter / Water Separator - To Install or Not?

While water/fuel separator filter is clean, the flow restriction is minumum, that's why is imperative to change them from time to time as they are not eternal.

Happy Boating

 

[robert graham]

Re: Fuel Filter / Water Separator - To Install or Not?

The fuel/water separator is probably the best one preventive maintenance item you can install on your motor. The standard ones are very low restriction, while the very fine(10 micron) units could become restrictive if very dirty and a high flow/HP motor. I use the Walmart/Attwood unit ($27) with no problems at all, dump water/debris now and then. Your motor might flow 15 gallons an hour at Wide Open Throttle, so maybe check that againt the clean filter flow rate. Check: Racor, for all the filters and flow rates. Good Luck!

 

[ondarvr]

Re: Fuel Filter / Water Separator - To Install or Not?

I have a very thirsty old 200 Evinrude and use one with no issues, it will empty a fuel tank faster than you could imagine. The guys on S&F have one thing in mind, and that's going as fast as possible and turning very high rpm's on modified engines. They also don't mind tinkering with stuff every weekend, so if they think not running the filter will let them go faster (true or not), then that's what they'll do.

 

[Chris1956]

Re: Fuel Filter / Water Separator - To Install or Not?

You do not need any other filter, if you have a water seperator. Actually, the other filter will contribute to fuel flow restriction and may cause an issue, and will not provide any additional benefit. Water seperators can be 40 Gal/hour or more, so restriction for your motor is not an issue. Be sure to use 3/8" ID brass fittings and fuel lines.

 

[robert graham]

Re: Fuel Filter / Water Separator - To Install or Not?

The under-cowl filter on my 90C Yamaha is just a plastic mesh screen and very unlikely to create a restriction. After I installed my Walmart/Attwood fuel/water separator several years ago there is very little water or debris in my under-cowl filter, but occasionally there will be a particle or two in that filter. Since a "particle" is all it takes to plug a jet then I just leave my under-cowl filter in place as a back-up, redundant filter. Good Luck!

 

[Chris1956]

Re: Fuel Filter / Water Separator - To Install or Not?

I do the same as Robert, and have kept the main strainer. I would skip any additional inline filter if you use a water separator.

 

[Dhadley]

Re: Fuel Filter / Water Separator - To Install or Not?

Fuel pressure is the key. We ran water seperators on our race boats. The stock powerheads ran a bit over 8000, the modified powerheads ran to about 12000 rpm. Never had a problem but we knew what fuel pressure we needed and had. Yes, adding anything in line may create a restriction so knowing what you're doing always helps. Some motors like the little 90 Merc 4 strokes are so close on pressure that a filter may indeed affect it.

 

[RMasters]

Re: Fuel Filter / Water Separator - To Install or Not?

My engine is almost 50 years old. The previous owner (for some 24 years) never used a Water Separator. Neither do I. I use clean fuel, have a fuel filter (thus simple) in the pickup tube in the tank, and a fuel filter at the motor.

Never had any issues. Would not even know how water could get inside my enclosed system (thus gasoline already contains some water).

 

[robert graham]

Re: Fuel Filter / Water Separator - To Install or Not?

My engine is almost 50 years old. The previous owner (for some 24 years) never used a Water Separator. Neither do I. I use clean fuel, have a fuel filter (thus simple) in the pickup tube in the tank, and a fuel filter at the motor.

Never had any issues. Would not even know how water could get inside my enclosed system (thus gasoline already contains some water).

The cartridge type fuel/water separators do a lot better job of filtration than the under-cowl filter/screens, and the cost of cleaning plugged carb jets or lean fuel conditions can be bad news$$$ The Walmart/Attwood fuel/water separator is $27, easy 2 screw installation, and great preventive maintenance. But if you're o.K. without it, Good Luck!

 

[Chris1956]

Re: Fuel Filter / Water Separator - To Install or Not?

Hey RM, Water will get into your closed system, when some gasoline station sells you water and pretends it is gasoline. If you are not going to run a water seperator, make sure to siphon the bottom of the tank a few times a year to get any water out. The ethanol in the gasoline has the unpleasant side effect of causing phase seperation where you get a water/alcohol layer and a gas layer. If the water/alcohol layer gets sucked into the motor, that is not too good!

 

[Zteven]

Re: Fuel Filter / Water Separator - To Install or Not?

The under-cowl filter on my 90C Yamaha is just a plastic mesh screen and very unlikely to create a restriction. After I installed my Walmart/Attwood fuel/water separator several years ago there is very little water or debris in my under-cowl filter, but occasionally there will be a particle or two in that filter. Since a "particle" is all it takes to plug a jet then I just leave my under-cowl filter in place as a back-up, redundant filter. Good Luck!

Thanks for all the comments guys. I picked up the Walmart filter and plumbed it in this week. Now I've got that filter and the under-cowl filter in place.