Fuel Filter basics - for outboard engines

[Marqus]

I'm working on a used 40HP Yamaha 2-stroke for a friend, and came across this gasoline filter installed by the previous owner - see attached photo. There's no fuel pressure gauge in the line.

It says "Spin on filter that removes 98.8% emulsified water and foreign particles as small as 10 microns".

Sounds fine. A couple of simple questions come up though, and I don't have answers - can anyone explain?

1) When water is captured by this filter, can you get rid of it in any way? I'm more familiar with inboard engine filters with drain bowls and taps to drain the water.

2) We know that different boats would accumulate water in the fuel at different rates depending on the owner's habits, fullness of tanks, day vs night temperature range and other factors. So how do you tell when enough water has accumulated to require filter replacement?

[Robert Tilbury]

I maybe wrong but thats a fuel filter ,,As in a particulate filter ,,Not a water separator ,,,,
My water separator ? Filter has a plastic bowl at the bottom to see water build up

[Lepke]

Most filters, diesel, gas and oil, will hold about 1 ounce of water. You change the filter to remove the water. There are disposable filters with a water drain. I have one on a diesel truck. Mine came with a clear bowl, but I changes to a full metal one later. There is a provision for a water sensor.

[Robert Tilbury]

Originally Posted by Lepke

Most filters, diesel, gas and oil, will hold about 1 ounce of water. You change the filter to remove the water. There are disposable filters with a water drain. I have one on a diesel truck. Mine came with a clear bowl, but I changes to a full metal one later. There is a provision for a water sensor.

I have the top one (R12T ) i empty if there is about 5 or so mm in the bottom ,

[Bean Counter]

In the Bahamas the other day I went to the aid of a local skiff with 70 HP who had run out of gas away from shore. I gave him my spare dinghy gas jug. He spun off the fuel filter and tipped out the contents, a watery sludge. He filled the filter with fresh fuel, poured it out again, and then filled again and spun it back on. Pumped some fuel through and away it went.

[Marqus]

Thanks Lepke and Robert, yes I'd prefer a drainable bowl too.

But I've seen quite of few of these spin-ons without bowls used with outboards, and they are sold by Mercury and Yamaha for such use.

And the label on this one says "Marine water separating fuel filter", so it does separate out water.

Still don't see how you tell how much water has been caught, and whether you can get any of it out by reverse flushing or any other way.

[Paul L]

I think for that type of filter you need to spin it off and dump it into a clear container, then check how much water settles out.

[Robert Tilbury]

Originally Posted by Marqus

Thanks Lepke and Robert, yes I'd prefer a drainable bowl too.

But I've seen quite of few of these spin-ons without bowls used with outboards, and they are sold by Mercury and Yamaha for such use.

And the label on this one says "Marine water separating fuel filter", so it does separate out water.

Still don't see how you tell how much water has been caught, and whether you can get any of it out by reverse flushing or any other way.

I think it filters emulsified water ? water in an emution with fuel ,,,, strainge wording hey ?

[flyingfin]

Unless you have bought really bad fuel, you will just get rid of the water each year when you throw out the old filter and buy a new one. Do not be tempted to save money and "clean" out the old filter and re-install it. Always carry at least two spares. You may not be able to find one quickly when you need it and may have to order replacements on line. Outboard filters are typically above deck and their cannisters will corrode quickly. When you get a hole in the cannister, the filter wont leak when running, instead you will suck air and the engine will cut out.

[Nightcrawler]

Originally Posted by flyingfin

Unless you have bought really bad fuel, you will just get rid of the water each year when you throw out the old filter and buy a new one. Do not be tempted to save money and "clean" out the old filter and re-install it. Always carry at least two spares. You may not be able to find one quickly when you need it and may have to order replacements on line. Outboard filters are typically above deck and their cannisters will corrode quickly. When you get a hole in the cannister, the filter wont leak when running, instead you will suck air and the engine will cut out.

What he said. . .

[a64pilot]

Many filters are designed that the filtering media will absorb water, it then clogs and blocks flow, they don’t separate, but absorb. I think Racors regular “aqua block” media does this.
A separator can get full and water will flow through

[seabreez]

Originally Posted by Lepke

Most filters, diesel, gas and oil, will hold about 1 ounce of water. You change the filter to remove the water. There are disposable filters with a water drain. I have one on a diesel truck. Mine came with a clear bowl, but I changes to a full metal one later. There is a provision for a water sensor.

I installed a Raycor similar to this one on a fuel injected outboard and never had problems with water. I drained the filter through the valve at the bottom only once. Works great.+++

[thinwater]

Ethanol (E10) vs. non-ethanol gas also makes a huge difference. In E10 the water is not emulsified but truly dissolved and the treatment is different.

In every case, if you are seeing material amounts of water you either have filler leaks or a poorly designed vent. The vent on a portable tank should be closed when not actively in use for a number of reasons. IF solar heating is a problem, cover it or get it out of the sun.

[Marqus]

Thanks, all useful replies. Also good tip about closing the vent.

As per BeanCounter and PaulL, I removed it an tipped out the contents into a clear container - see attached photos.

No evidence of water, which I would imagine would settle at the bottom.
But more dirt particles than I would like to see, or maybe it's not that bad.

The gasoline (no oil mixed in) sees more yellow than it should be. Does unleaded gasoline (zero ethanol) typically go yellow like this over a few months?

[thinwater]

Originally Posted by Marqus

Thanks, all useful replies. Also good tip about closing the vent.

As per BeanCounter and PaulL, I removed it an tipped out the contents into a clear container - see attached photos.

No evidence of water, which I would imagine would settle at the bottom.
But more dirt particles than I would like to see, or maybe it's not that bad.

The gasoline (no oil mixed in) sees more yellow than it should be. Does unleaded gasoline (zero ethanol) typically go yellow like this over a few months?

You did not say if there was ethanol in the gas. It matters.

There are two things that make it go yellow.

1. Air exposure. Close the vent.
2. Exposure to copper and zinc ions related to corrosion. These are well known to catalize polymerization in petroleum products and are for bidden in standby generator fuel systems installations (google any major diesel generation manufacturer). The cure is an effective corrosion inhibitor, such as Merc Quick Stor or Biobor EB.

Ethanol aggravates cause #2, but so do even tiny (invisible) amounts of water. Keep the vent closed.



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