Help Needed: Enging Losing Fuel Supply

[CTsalt12]

My engine runs perfectly fine at idle and high idle.  Once I go up to cruising speed around 4,000 RPM I've encountered a problem where the engine slowly dies after a few minutes on plane.  The fuel ball will be completely deflated, so it's apparently not getting enough fuel.  

Now, I have an a kinked fuel vent, but this can't be the problem.  I've nbeen using the boat 3-4 times a week for 3 months, sometimes cruising for up to an hour without this problem, the kinked fuel vent only seems to affect the fill up.  

Any ideas?

[seabob4]

Well, CB will be along suggesting the search function, but I'll put my .02 in...anti-syphon valve in the pickup?

[Blue Agave]

IMO its the vent line!  Need to resolve the kink in the vent.

[flounderpounder225]

IMO its the vent line!  Need to resolve the kink in the vent.

I would agree, especially considering the fuel level in the tank, you said you never had the problem before, but over time the kink could soften and get tighter, also, fuel level and amount of air space above the fuel would effect how quickly the vacuum on the line would present itself.  More air space above the fuel = longer run time before vacuum lock... fix the obvious first, then try the other stuff.

[CTsalt12]

Ok, I may have to bite the bullet.  

One question though, It's been mentioned in a few places that you can tell if venting is the problem by running the engine with the fillup cap off.  Will this in fact indicate if venting is the problem?  Because I've tried that already to no avail.

[Blue Agave]

The fact that your fuel bulb is collapsing indicates you have a vent problem.  Why do you believe you have a kink in the vent line?  Have you changed the vent it self?

[CTsalt12]

I can feel and see (using a mirror) the kink in the vent, right where it meets the tank.  And I can't put in fuel at a high rate or it spits up.  I have not changed the vent itself. I assume you mean the external vent outside of the hull?

[Blue Agave]

Yes the vent outside the hull.  If the vent is clogged or corroded it may be causing the kink in the vent hose.  You definitely have a vent issue, if the vent is easier to get to than the kink change the vent and see if that resolves the kink in the hose.  If not you are going to have to deal with that kink.

[flounderpounder225]

Ok, I may have to bite the bullet.  

One question though, It's been mentioned in a few places that you can tell if venting is the problem by running the engine with the fillup cap off.  Will this in fact indicate if venting is the problem?  Because I've tried that already to no avail.

Ok, the kink is a problem, but if you have run with the fill cap off and still collapses the bulb... either bad primer bulb, or as Bob stated probably the anti-siphon valve in the pick up tube.

[Capt. Bob]

Well, CB will be along suggesting the search function, but I'll put my .02 in...anti-syphon valve in the pickup?

Seems we traveled this road earlier.
viewtopic.php?p=75339#p75339

[John Jones]

Ok, I may have to bite the bullet.  

One question though, It's been mentioned in a few places that you can tell if venting is the problem by running the engine with the fillup cap off.  Will this in fact indicate if venting is the problem?  Because I've tried that already to no avail.

Ok, the kink is a problem, but if you have run with the fill cap off and still collapses the bulb... either bad primer bulb, or as Bob stated probably the anti-siphon valve in the pick up tube.

This

[kraw2]

Remove the anti siphon fitting. It's not needed. Replace it with an aluminum hose barb fitting.

[CTsalt12]

Well found a few things out working on it this weekend.  1-Fuel vent seems to be impeded by a vent screen that pulled through and was gunked up with debris.  Hard to say if this was enough to block airflow completely.  Took that out and put in new screens.  I did not put on a elbow piece because it seemed to be breathing just fine with the blocked screen taken out.  

Found out I have a 25 gallon Moeller standard tank.  http://www.moellermarine.com/sites/moel ... 599-r3.pdf
Doesn't appear to have a anti siphon valve?  Just got off the phone with a Moeller rep who  informed me there is a screen at the  bottom of the pickup tube in the tank which could've gotten gunked up.  Really wish I pulled this when I had the deck up, before I sealed it again.  Dumb dumb dumb.  

I tried a trick that's supposed to tell you if you have a fuel hose issue, which is taking off hose that goes from primer to engine, plugging primer bulb with finger and deflating.  It re-inflated pretty quickly, so I don't think the hoses are in fact clogged.  
Didn't get a chance to take it for a ride because of time, gonna try that tomorrow night, it should be working just fine though.  

If this doesn't work, is the next step to change fuel / water separator?

[saltfly]

First you have to go about this in a logical manner. Not jumping all over the place. You said your bulb is going flat. Well that tells you the fuel pump is working and is sucking gas fine or your bulb would not be going flat. So every thing is clear to the filter. So next logical thing is the filter. New filter will solve that . If it is still not working. Check the fuel line to the tank. If that is fine its in the tank. You can check the faul line and the screen at the bottom of you tank, by blowing about 5 psi of air down the line. If the screen is clogged. This will open it so fuel will pull throw. If this fixes the problem, it is only a temporary fix. It will clog again. So you will have to drain the tank and have it cleaned.  But you have to get the vent fixed. Or you will have this problem again. The pump is working way to hard trying to get gas up the line, and to do this in a closed tank. It must vent properly.