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Question about inline fuel filters. Does it matter how they "hang"?

D

djcamera

Contributing Member
Mercury 75hp 2 stroke. I added an fuel filter on the line about 18 inches before the engine. Not the 'glass' type, but this type:

ffilt.jpg
Question: I see that it does not get completely full of fuel, rather the fuel level stays about half, no matter how I prime it. Is that normal? Also, what about orientation? Does it matter if it's on its side, tipped one way or the other, or does it need to be upright to work best?
 
Personally, I NEVER install a fuel filter before the fuel pump on a outboard. The vacuum produced by the typical OB pump is not very great and can cause fuel starvation at times, especially if you get a crappy tank of gas from some marina.

Jeff
 
fastjeff said:
Personally, I NEVER install a fuel filter before the fuel pump on a outboard. The vacuum produced by the typical OB pump is not very great and can cause fuel starvation at times, especially if you get a crappy tank of gas from some marina.

Jeff
Click to expand...

I do get some rough idling sometimes that improves when I pump the primer bulb. Maybe that's the struggle through the filter? So you don't filter your fuel at all? Do you pump gas into your tanks through a filter?
 
I put the filters AFTER the fuel pump. Merc did this with every motor (long as I can recall).

Now, watch some wiz kid point out one that they didn't!

Jeff
 
fastjeff said:
I put the filters AFTER the fuel pump.
Click to expand...

I've got a little cone-shaped screen filter about the size of a half-dollar in a housing where the fuel line goes into the fuel pump. That's the only built-in filter on my motor, and from what I see, a short bit of line goes straight to the carbs, so no room for anything to add, like a fuel filter AFTER the pump. My motor is on the older side, from '86.
 
The 15 micron wire mesh filter BEFORE the pump has been used for years with no problems if you keep them clean. You did not see inline filters in motor till Merc changed fuel pump design....
 
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