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Catalina/Capri 25/250 Sailor's Forums

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Stupid question for the day, fuel filter direction

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 05/30/2011 : 11:21:57

I'm replacing the fuel filter on my Tohatsu due to the rust & water that was pumped through it from my rusted out fuel can. I couldn't find a direct replacement part, so I bought this instead: [url="http://www.amazon.com/INLINE-FUEL-FILTER-Sierra-18-7828/dp/B000LN2HI4"]Sierra fuel filter[/url].

Here's the stupid question: there are no directional arrows on the filter and no directions on the card it came on, so which end is which? I'm guessing that the wide end (left side of photograph) goes toward the fuel tank, and the narrow end toward the carburetor? This makes sense to me, more surface area exposed to filtration and contaminants can fall away into the base of the filter cone out of the fuel stream.

Does this seem right to you? Is there a rule of thumb you can use for determining the right direction? Most other filters I've seen have directional arrows, so this has never come up before.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 05/30/2011 : 12:36:41

Stupid answer of the day - my guess would be the fuel flows towards the left (in your picture) as the top of the screen appears to be on the right . . . dirt and rust would accumulate outside the screen?

I'm curious - let us know!

Edited by - OJ on 05/30/2011 12:37:37

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 05/30/2011 : 13:12:38

I thought the filters usually ran such that the fuel was forced from the inside out, or the opposite of what OJ said. Of course I am equally clueless, so so far you have a score of:

Stupid questions, 1
Stupid answers, 2

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 05/30/2011 : 13:16:36

Um...OK, one vote says right to left, another left to right. We need a tie breaker guys... Any mechanics out there?

Sorry, I just laughed out loud when I saw your two answers...

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OJ
Master Marine Consultant

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Response Posted - 05/30/2011 : 13:43:25

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Prospector
 I thought the filters usually ran such that the fuel was forced from the inside out . . .<hr height="1" noshade id="quote"></blockquote id="quote">I would normally agree but the screen in this unit is so small that I would think it would become clogged pretty quickly?

I had one of these installed on a 2 hp Johnson I sold this spring and I'll be darned if I can remember which way it pointed!

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Stinkpotter
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Djibouti
9076 Posts

Response Posted - 05/30/2011 : 13:44:43

Stupid question number 2 (to tie with the answers): Can you find the words In and Out imprinted anywhere?

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 05/30/2011 : 13:48:11

There is nothing printed on the filter anywhere, no arrows, no lettering, no nothing.

I agree that it looks like the smaller end would plug quickly if the fuel flow was from right to left in the photo above, that's why I'm leaning toward left to right for fuel flow.

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Stinkpotter
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Djibouti
9076 Posts

Response Posted - 05/30/2011 : 13:59:33

In your application, the fuel is being sucked through by the engine. The filter should be oriented to that suction doesn't collapse the element in the middle, but rather holds it open. I can't tell from the picture which way that would be, but that would be my criterion.

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Prospector
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Canada
3159 Posts

Response Posted - 05/30/2011 : 16:02:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkpotter
 In your application, the fuel is being sucked through by the engine. The filter should be oriented to that suction doesn't collapse the element in the middle, but rather holds it open. I can't tell from the picture which way that would be, but that would be my criterion.
<hr height="1" noshade id="quote"></blockquote id="quote">

That is what I was thinking as well. If crud builds up on the outside of the filter, it will collapse inwards. If crud builds up inside the cone, it will just keep catching it in the bottom of the "funnel"

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britinusa
Web Editor

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USA
5404 Posts

Response Posted - 05/30/2011 : 16:05:37

I'm guessing this is for 9.8hp tohatsu 4 stroke: [url="http://www.tohatsuoutboardparts.com/Parts-Catalogs/Parts%20Catalog%20MFS8A3-9.8A3%20(2006)%20-%20(00221051-2).pdf"]here's the manual[/url]
The fuel filter is on page 7/8

Paul

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Stinkpotter
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Djibouti
9076 Posts

Response Posted - 05/30/2011 : 19:42:05

And if you really want to protect it from the water and crud that your fuel suppliers might "give" you, a [url="http://im1.shutterfly.com/media/47b6d627b3127ccece99c71989b500000010O08QatXLNw3ag9vPgA/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/"]Raco separator/filter[/url], especially with a glass bowl and drain, is the best bet.

Edited by - Stinkpotter on 05/30/2011 19:44:29

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 05/30/2011 : 19:44:59

I think that you will find that filters orient so that water and debris collects in the open volume of the chamber. Fuel flow from inside out has little collection volume and no visible check; flow from inside out could also lead to a ruptured element and a loss of filtration if the filter clogs as opposed to just cutting fuel flow. It is clear so you can see the filter's condition and should be oriented that way. I have never installed a universal filter on a small engine that didn't have some indication of flow direction, nor have I seen one that flows inside to outside.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 05/30/2011 : 22:21:46

So I ended up reversing myself and installed it so that the fuel flows from right to left in the picture (from the pointy end of the cone toward the wide end) for much the same reasons as stated above. I figured the crap would settle out into the wide end. I didn't get a chance to test it yesterday (see my post on the 4 pole connector elsewhere on the site), but I will tomorrow. Maybe something will go right for a change.

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OJ
Master Marine Consultant

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4382 Posts

Response Posted - 05/31/2011 : 04:02:26

Or this one . . .

Photo compliments of Tom Gauntt

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dmpilc
Master Marine Consultant

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4593 Posts

Response Posted - 05/31/2011 : 09:50:21

David, I believe you did it correctly, right to left in your pic above. The fuel needs to flow into the filter case and go through the filter element from outside toward the center of the element. That way, any junk stopped will be visible. also, that allows a larger filtering surface to stop dirt, etc.

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