Bogging issue

[Jjp12496]

So I’m having trouble here and can really use the help. I have a mercruiser 4.3 alpha one. I rebuilt the carb last year took it out and the boat ran great. It starts up and idles good and reves fine. I can run the boat hard for 20 minutes or so tubing or getting across the lake . Then it starts bogging and cutting out. I have a clear inline filter usually it’s about half full and I noticed it’s completely filled with gas. So I popped it off it shot gas out I put it back on and boat runs great for ten more minutes. Then same thing. Anyone have any suggestions? I assume it has to be carb. Could float level effect this?

 

[dubs283]

If the clear in line filter is between the pump and carburetor you should abate it

The only filters should be between the fuel tank and the fuel pump. One water separator is sufficient. If the fuel pump is mechanical there should be a filter in the housing as well

 

[Scott06]

So I’m having trouble here and can really use the help. I have a mercruiser 4.3 alpha one. I rebuilt the carb last year took it out and the boat ran great. It starts up and idles good and reves fine. I can run the boat hard for 20 minutes or so tubing or getting across the lake . Then it starts bogging and cutting out. I have a clear inline filter usually it’s about half full and I noticed it’s completely filled with gas. So I popped it off it shot gas out I put it back on and boat runs great for ten more minutes. Then same thing. Anyone have any suggestions? I assume it has to be carb. Could float level effect this?

Try taking the fuel filler cap off when this happens. By what you describe you may a have a plugged fuel tank vent eventually the tank gets under enough of a vacuum to stop letting fuel out to carb. Could also check the pick up tube some have a sock or internal screen that could get clogged. Would also look for splits in fuel line suction side

Also agree that the clear fuel filter is not safe in a marine application.

If you have a outboard tank you could rig that up and run it on the small tank to confirm it is a boat fuel tank delivery issue

 

[Jjp12496]

Try taking the fuel filler cap off when this happens. By what you describe you may a have a plugged fuel tank vent eventually the tank gets under enough of a vacuum to stop letting fuel out to carb. Could also check the pick up tube some have a sock or internal screen that could get clogged. Would also look for splits in fuel line suction side

Also agree that the clear fuel filter is not safe in a marine application.

If you have a outboard tank you could rig that up and run it on the small tank to confirm it is a boat fuel tank delivery issue

I appreciate the comment I will remove the clear fuel filter . You don’t think it would be anything with the floats? I was thinking the gas tank wasn’t venting properly as well so I took the vent hose out and it’s all open. It’s a pain to diagnose because you have to be running it at full speed for a decent amount before it acts up. Soon as I pull the line off let some pressure out it runs fine .

 

[Scott06]

I appreciate the comment I will remove the clear fuel filter . You don’t think it would be anything with the floats? I was thinking the gas tank wasn’t venting properly as well so I took the vent hose out and it’s all open. It’s a pain to diagnose because you have to be running it at full speed for a decent amount before it acts up. Soon as I pull the line off let some pressure out it runs fine .

what line do you pull off? The fuel line ?
of that is the case then you either have too much fuel pressure or a bad float or needle and seat

 

[alldodge]

Soon as I pull the line off let some pressure out it runs fine .

Removing the fuel line off the carb is just giving the fuel tank time to suck in some air. Your first run is 20 minutes, pulling the line off and you get 10 minutes. Open the gas cap as Scott06 mentioned, you should go back to 20 minutes

If this works then as was said it's the tank vent line is your issue

 

[Jjp12496]

what line do you pull off? The fuel line ?
of that is the case then you either have too much fuel pressure or a bad float or needle and seat

Yes I pull off the fuel like that goes into the carb it like releases pressure then the boat will run again good for a bit. And repeat .

 

[Jjp12496]

Yes I pull off the fuel like that goes into the carb it like releases pressure then the boat will run again good for a bit. And repeat .

What would cause so much pressure?

 

[Jjp12496]

What would cause so much pressure?

Could it be from the float level being to low it’s not letting fuel in fast enough or something?

 

[alldodge]

It doesn't take much pressure to see something. Carb would be 4-7 psi

When the line comes off is it full of fuel or air?

If fuel pump the throttle and see if fuel squirts down the carb