air bubbles in inline filter

[gussbuster]

Hey guys. 1990 150hp Force. I put an inline filter in and I notice it fills with fuel when running then intermittently will fill with air bubbles. Almost looks like a gurgling toilet flushing. At the end of last season I had problems at WOT, it would lose power and then come back up. I can only assume this is the reason why? I have replaced all lines and checked clamps and they all seem ok. Obvisouly air is getting in somewhere. Any tips on where to start?

 

[SweeperForce]

Re: air bubbles in inline filter

Check your fuel pumps. Make sure all the gaskets, seals and diaphragms are in good shape. There is a disk filter on the fuel pump, make sure it is clean. Does your squeeze bulb have any signs of dryrot?

Tom

 

[jerryjerry05]

Re: air bubbles in inline filter

Do what Tom says then check the hose/squeezie.Any inline connectors?Remove them.Ethanol or age makes them go bad.They start sucking air.
Just for GP rebuild both pumps,make sure the gasket behind the pumps are good.
ALL clamps tight.J

 

[BobList]

Re: air bubbles in inline filter

I'm not so sure that's a problem.. I have a big inline filter that is clear... when the bulb is pumped up, it only fills half way. Under power, even at full throttle, it looks nearly empty... the fuel is flowing in ok, and it's getting sucked into the engine.. I have no problems with fuel.
The pump is PULLING fuel from the tank.. under these conditions, they are not air bubbles, but cavitation (vacuum). I feel the filter paper has enough restriction in it to cause the vacuum behind it. ( tank side). If we used pressure in the tank, or had a fuel pump PUSHING fuel into the filter, then yes, air would be a problem.
I was confused myself when I first saw my filter "empty", and filled with empty space. I would like to think my filter should be full.. but it runs ok. Boat techs chime in here....... Is this correct?
But, as usual, I state the fact I'm not a boat mechanic, I'm a car guy... fuel delivery is way different!

Bob List

 

[gussbuster]

Re: air bubbles in inline filter

Thanks for the response guys. The bulb is brand new along with the lines. I checked all inline connections and they seem ok. I guess it is possible that the bubbling down is normal Bob? I just want to be sure before she hits the water.

 

[BobList]

Re: air bubbles in inline filter

verify this with a boat mechanic... when I use a vacuum bleeder on brakes with a clear tube... bubbles are normal... it's not air, it's cavitation bubbles I see. I feel the same scenario is happening in the fuel lines. Especially if it seems to run well.

Bob List

 

[BobList]

Re: air bubbles in inline filter

Gonna bump this up top again.. I'm still curious as to what is normal. I have a 2" diameter clear in line filter between the fuel bulb and engine, and it is never "full".. even with a solid bulb. After running a bit, it appears empty, but you can see fuel comin in to the filter in a steady stream, but it looks empty. Looking for marine experts who state this is normal.
Also, is there any rules about the bulb or filter being above or below the tank level?

Just curious,

Bob List