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Discussion Starter #1
Installed a fuel water separating filter for my 2010 Merc 90 Opti. Engine starts and idles fine but when I got to WOT the engine just sputters and dies as I getup on plane. I think it is a fuel pressure issue but I wanted to see what the brain trust may know. Please share what you think it may be and how I can remedy the issue.

Thanks,
Chad
 

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Discussion Starter #3
Probably sucking air or trapped air in fuel system.
I only have about 10 gal(28 gal tank I believe) in the boat right now. So should I -
1) Fill it up completely
if not
2) how can I get the air out?
 

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You need to check all the hose clamps from when you installed the filter. Make sure they are all tight. Also, if you didn’t replace the fuel hose that runs through the boat, you may have cracked it when cutting and installing the filter, as the lines get brittle over time, or collapse internally and the inner liner doesn’t allow full flow and becomes a restriction as the flow rate increases with engine rpm. You can check by Bypassing parts of the system such as the primer bulb and fuel water separator to find restrictions or air gaps that may be allowing the outboard fuel pump to suck some air.
 

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Discussion Starter #5
Hose is in good shape, checked before I cut it. I will check the fittings once again. I'm leaning towards what Smack mentioned and this there is are in the lines somewhere.
 
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If you have a screw on type filter, did you put a coat of grease on the washer before installing it? These days the alcohol in fuel can attack the washer (or gasket), and soften it so that you don’t have an air tight seal. If that’s what’s happened you’ll get enough fuel to be able to start and idle- but not enough to get up on plane and run... A slight leak anywhere along your fuel anywhere between tank and motor can cause the same problem...
 

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Plug off the line at the tank. Use a Mightyvac to put a vacuum on the line and see if it leaks off. if it doesn't then the filter assembly may be to much of a restriction or you have a faulty / inefficient pump that deal with the new head pressure. An easy way to check that would be bypassing the filter with a barb fitting and see if the problem is resolved. A Mightyvac can be rented at some auto part stores. Hope this helps.
 

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Well said Smack... that's the first thing a pro does before getting into messing with the fuel system - make sure it's not the engine with a problem...
 

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Discussion Starter #11
Thanks everyone for the input. I'm going to double check fittings, hose clamps, etc. today. Going to re-prime the line and hope for the best. I didn't grease the gasket on the filter but I did rub some 2 stroke oil on it (like when doing an auto oil change). I'm actually running E free fuel right now due to the water in the tank I've already experienced.
 

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Had the same problem on my larger boats 150 E-Tec. Turned out to be a defective water separator. If you have the old one put it back on a see if it helps.

My mechanic said he's seen a big increase in defective seps being outsourced from China.
 

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Discussion Starter #14
Had the same problem on my larger boats 150 E-Tec. Turned out to be a defective water separator. If you have the old one put it back on a see if it helps.

My mechanic said he's seen a big increase in defective seps being outsourced from China.
I just installed the setup on the boat as it did not have one at all. I have an extra filter, maybe I'll try that.
 
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Discussion Starter #15
Had the exact same problem when I Changed fuel water separator on my 40 mercury, Did what topnative2 said was able to push all the air out of the system. Motor ran like normal with no issues after that.
I'm hoping that it is that easy for sure. I just want to get out, go fast and catch fish.
 

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I just installed the setup on the boat as it did not have one at all. I have an extra filter, maybe I'll try that.
You may have sucked up a bunch of h2o which will cut the fuel flow down to where u can't go fast...dump it into a jar to see if it is a water issue if it is not a clear bowl model...since u did not have a water separator on it before my money is on this
 

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you guys are reminding me that I probably need to change both of mine. I always write the date on a new filter with a sharpie, will need to go check.
 

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Discussion Starter #19
You may have sucked up a bunch of h2o which will cut the fuel flow down to where u can't go fast...dump it into a jar to see if it is a water issue if it is not a clear bowl model...since u did not have a water separator on it before my money is on this
I drained the tank before I installed the filter setup but I'll double check that too.

On the subject of changing filters, the one that I am using states it is reusable. I thought hat was odd because of what it is used for. I have a second new filter and I may go ahead and just swap filter for now.
 

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We use to shake the water out when the filter got filled.It is better to get the ones w/ the clear bowl because u can see the water and then open the relief knob and tap it till the water is gone and re-tighten.

The filters can be used for awhile they are pretty tough.
 
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