# carb vs fuel delivery? question



## Brett (Jul 16, 2008)

There is a simple way to pressure test an outboard fuel pump.
One I learned from a shade tree mechanic years ago.
After activating the kill switch and removing the spark plugs so the engine couldn't start,
he'd remove the short fuel line from the fuel pump to the carburetor,
and replace with a longer hose. This would allow him to extend the end of the hose
from the output side of the pump into a wide mouth container.
With a second person assisting, he'd place his thumb over the end
of the hose from the pump, then using the fuel line primer bulb,
fill the fuel system with fuel all the way to his thumb.
This removed all the air out of the pump and fuel lines.
Then, with his thumb held tightly over the end of the hose,
the assistant would pull the starter cord a few times
letting pressure build up in the fuel line, held in check by his thumb.
Aiming the hose into the container, he'd let his thumb lift
slightly from the end of the hose, directing a jet of pressurized fuel
into the container. If there was no jet of fuel, a second attempt would be made.
If still no stream of fuel squirted past his thumb, then the pump needed rebuilding.


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## KeepingItSimple (Mar 20, 2011)

From what I see going through the glass cylinder fuel filter and from watching how slowly the fuel drains out of the other plastic filter on the side of the motor just before the pump, my suspicion that there's a high pressure stream is nil. I think I'm gonna spend the $35 for the rubber parts to rebuild the fuel pump.
Thank you.
Alex V


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## iMacattack (Dec 11, 2006)

Also look at the anti siphon valve at the fuel tank. This was a common problem (I had to replace mine on the 17T I owned). I thought I was having a fuel problem and it turned out to be the anti siphon valve. 

http://www.microskiff.com/cgi-bin/yabb2/YaBB.pl?num=1247153549/31


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## KeepingItSimple (Mar 20, 2011)

If it is the antisiphon valve, would I still be able to pump fuel through easily with the ball? Thank you.

Alex V


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## cutrunner (Jun 8, 2010)

Another way to check the fuel pump on your motor is to unbolt it from the side of the motor with the two ten millimeter bolts that hold it on, squeeze the primer bulb, if no fuel shoots out of the diaphram , its good. If fuel shoots out replace it.


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## KeepingItSimple (Mar 20, 2011)

Someone on another forum suggested that it's the idling jets/passage ways. Thoughts?

Thank you.
Alex V


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## Brett (Jul 16, 2008)

It's a fuel "system", any part can affect how the engine runs.
From your description so far, it sounds like an air leak,
somewhere between the fuel pick up and the carb.
If you don't find an air leak and the fuel pump is ok,
then you get to look at the carb, linkages and ignition system.

Sounds like fun to me.... 

How old is the boat and outboard? :-?


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## iMacattack (Dec 11, 2006)

> If it is the antisiphon valve, would I still be able to pump fuel through easily with the ball?


Yes you would. Bonus point is that changing the anti-siphon valve is cheep, about $10 or less and easy.

If it has not been done it might be worth a look.


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## KeepingItSimple (Mar 20, 2011)

Fair enough. I'll change the fp guts and do the antisiphon thing. It's a 2001. Due for some maintenance I suppose. Those things are pretty easy. Totally rebuilding the carbs is a bit more work - I think I'll hold on that for now. Shoot, just taking the carbs completely off is no joke with the oil tank and all those tubes and the couple of linkage points.

Alex V.


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## Brett (Jul 16, 2008)

10 years old, yeah, it's time for a fuel system rebuild.
That was a pre-E10 fuel system and engine.
No telling what you'll find when you start checking closely.
If/when you replace parts, make sure they're ethanol compatible.


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