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Old 10-05-2012, 00:47   #1
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In line fuel filter for 2 stroke outboard

I just got a pile of gunge out of the carby of my 20hp outboard that had somehow got past the factory gauze filter that is under the engine cowling.

I thought that an inline PRE filter like this

between primer bulb and gauze filter would be a good addition and spoke to an outboard mech. just to check.

He tells me a big no no claiming that the paper filter will suck up the oil changing the oil ratio of the mix.

Anyone heard of this?
Cant really find a definite answer online and feel it may be an old wives tale.
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Old 10-05-2012, 03:42   #2
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Re: In line fuel filter for 2 stroke outboard

I have used that filter successfully many times, no problem.
If you are using that ethanol crap we burn up here in the top part of the world, it may not become gunk until it gets in the carb, and evaporates first the real stuff, then the ethanol, leaving behind the brown varnish scale.
Just saved 2 2hp Yamahas that were discarded for this same reason.
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Old 10-05-2012, 06:36   #3
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Re: In line fuel filter for 2 stroke outboard

Nonsense. I'm a chemical engineer with 29 years in the lube business. There is nothing in an additive package and no part of the base oil that can be removed by 10 micron filters; filtration to 0.005 microns, or 2,000 times finer, would be required to have that effect. If you think about the math, that's like trying to filter out sand with an open garage door.

I've run a small suplimental filter like that on my dingy kicker for years (a lawn mower filter works on smaller ones) and it helps. So does keeping the tank full (no breathing), vents close (if practical), and using a corrosion inhibiting storage additive like Stabil, Merc Store-&-Start, Biobor-Ethanol, or Valv-Tech Ethanol. Most of the grunge is aluminum corrosion products and water emulsion.
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Old 10-05-2012, 07:39   #4
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Re: In line fuel filter for 2 stroke outboard

Quote:
Originally Posted by thinwater View Post
Nonsense. I'm a chemical engineer with 29 years in the lube business. There is nothing in an additive package and no part of the base oil that can be removed by 10 micron filters; filtration to 0.005 microns, or 2,000 times finer, would be required to have that effect. If you think about the math, that's like trying to filter out sand with an open garage door.
Thats what I thought as well but what would I know
I kept thinking 25 litres of fuel, 500ml of oil and a filter the size of an egg, if it was to filter the oil out surely it would be clogged in minutes.

I have had several people today tell me that this style is the minimum

and definitely no paper.

I dont have a problem buying the more expensive one if I have to, but if I can use one for$20 less

Quote:
I've run a small suplimental filter like that on my dingy kicker for years (a lawn mower filter works on smaller ones) and it helps.
Definitely paper elements on two strokers?


Quote:
Most of the grunge is aluminum corrosion products and water emulsion.
25 litre plastic tank
I think the crud has come about by the fuel sitting for a while before I bought the boat and motor and since then I have ran a couple of tanks and a lot of the associated crud though the system.
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Old 10-05-2012, 08:02   #5
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Re: In line fuel filter for 2 stroke outboard

Quote:
Originally Posted by cat man do View Post
I just got a pile of gunge out of the carby of my 20hp outboard that had somehow got past the factory gauze filter that is under the engine cowling.

I thought that an inline PRE filter like this

between primer bulb and gauze filter would be a good addition and spoke to an outboard mech. just to check.

He tells me a big no no claiming that the paper filter will suck up the oil changing the oil ratio of the mix.

Anyone heard of this?
Cant really find a definite answer online and feel it may be an old wives tale.
I design and build very light aircraft that use 2-stroke engines,and would never use paper filters or a primer bulb.The filters with a stone type of filter would be a better choice and a length of fuel tube(instead of a primer bulb) that you blow into would keep your carb from leaning out should your bulb get a small pin hole in it....primer bulbs are for 4-strocks, they will ruin a good engine in seconds with just a small pin hole...maybe its not a big deal if your not 200 ft off the ground or on a lee shore...DVC
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Old 10-05-2012, 08:21   #6
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Re: In line fuel filter for 2 stroke outboard

either filter will do wonders for your outboard. i have used each at different times. is important to keep the crud out of the carb--or ye will be rebuilding it every 2 weeks, as i used to ---after the addition of a filter,i was trouble free for years. go for it. either one is good.
andNO, the filter will NOT "change the mix" nor willit "suck up all the oil" as your friend sed. i used them in both 2 stroke engines and 4 strokes with EXCELLENT success, and kept my need for mechanic to a minimum--he is prolly mourning the potential loss of business.
my former outboard expert (sunset marine, san diego) said to USE a filtwr so i wouldnt have to pay him so often. it works.
fire your mechanic.
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Old 10-05-2012, 08:28   #7
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Re: In line fuel filter for 2 stroke outboard

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Originally Posted by cat man do View Post
I have had several people today tell me that this style is the minimum

and definitely no paper.
That's a decent filter, but they turn to white powdery zinc crap in no time when exposed to salt.
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Old 10-05-2012, 08:36   #8
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Re: In line fuel filter for 2 stroke outboard

sailmonkey--i had one of those for 2 yrs before it crudded into powder, and then it still worked--was cosmetic only. is not an issue for function, as i recall. if you keep it out of the bottom of the leaky dink, you will be ok.
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Old 10-05-2012, 08:42   #9
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Re: In line fuel filter for 2 stroke outboard

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Originally Posted by zeehag View Post
sailmonkey--i had one of those for 2 yrs before it crudded into powder, and then it still worked--was cosmetic only. is not an issue for function, as i recall. if you keep it out of the bottom of the leaky dink, you will be ok.
I got to the 6 month mark when the chrome was coming off in sheets and the ends turned to powder.....it actually didn't come apart for another 3 months.
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Old 10-05-2012, 15:23   #10
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Re: In line fuel filter for 2 stroke outboard

Wonderful advice guy's, it's just like going on trip advisor looking at hotels.

Half say its the best hotel they have ever stayed at and the rest say its the worst hotel they have ever stayed at and you can do better for less, but never say where.
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Old 10-05-2012, 15:26   #11
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Re: In line fuel filter for 2 stroke outboard

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Originally Posted by zeehag View Post
the filter will NOT "change the mix" nor willit "suck up all the oil" as your friend sed.
It was not my friend, it was a mechanic.
In fact it was several mechanics.
There must be a conspiracy against paper elements down here.
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Old 10-05-2012, 15:34   #12
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Re: In line fuel filter for 2 stroke outboard

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Originally Posted by tropicalescape View Post
I design and build very light aircraft that use 2-stroke engines,and would never use paper filters or a primer bulb.The filters with a stone type of filter would be a better choice and a length of fuel tube(instead of a primer bulb) that you blow into would keep your carb from leaning out should your bulb get a small pin hole in it....primer bulbs are for 4-strocks, they will ruin a good engine in seconds with just a small pin hole...maybe its not a big deal if your not 200 ft off the ground or on a lee shore...DVC

I don't understand how a small pin hole (this would allow some air in the line?) could ruin an engine. Is that after the crash/grounding?

I have never had a bulb leak or fail either, but then when I see it needs replacing I do that.
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Old 10-05-2012, 15:37   #13
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Re: In line fuel filter for 2 stroke outboard

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I don't understand how a small pin hole (this would allow some air in the line?) could ruin an engine. Is that after the crash/grounding?

I have never had a bulb leak or fail either, but then when I see it needs replacing I do that.
Yeah, I didn't follow that either.....an air leak in the fuel line will just deliver air to the float bowl with the fuel, in an extreme case I suppose that if just the right amount of air is being sucked in to cause the engine to still run, but poorly and lean there would be a problem.....but there are a lot of things in this world to worry about, and I am not going to let this be one.
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Old 10-05-2012, 15:41   #14
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Re: In line fuel filter for 2 stroke outboard

No pleated or paper elements? What do we suppose are in automotive elements and in Raycors? Pleated elements.

Why not in an ultralight? You have to think about the application. Marine paper elements are design to expand (cellulose does this when it sees water) and blind when wet. This prevents engine damage. In a plane, very bad, in a boat, the desired result in most cases. Different horses for different courses; the aviation solution is different, but perhaps not better.

Yes, you should carry a spare (filter and primer). If the primer bulb goes, a hose mender and knife would fix it in 20 seconds, or a simple replacement. Same with the element style you are suggesting. The lee shore argument is off the point. Even if there is a lee shore, I need to know about the water in the fuel, which is MUCH more likely in a boat.

No, I would NOT use the clear filter. Your first suggestion is proven.

FYI, this is what I now do on my outboard powered cat (2 x 9.9 hp Yamaha)...
Sail Delmarva: Gasoline Filtration... and Vent Filtration Too?
There is also a lawn mower element under the cowling.

... and on my tender I use lawn mower elements (too small for 20hp). I can change them in seconds and they only cost $2.50, though they do last over a year. That engine had no filter (strainer inside the fuel tank) when I got it (3.5 hp Merc).
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Old 10-05-2012, 15:57   #15
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Re: In line fuel filter for 2 stroke outboard

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No pleated or paper elements? What do we suppose are in automotive elements and in Raycors? Pleated elements.
Cars are not 2 stroke

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FYI, this is what I now do on my outboard powered cat (2 x 9.9 hp Yamaha)
Neither are your 9.9's

I had one of these for my 9.9 plus the cheap pleated paper filter, but of course they are 4 strokes so no oil.
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