WOT Carb help

[trainwrecker22]

I have a 96 350 with a mercarb 2 barrel. The issue is when i run at WOT I can only run for 7-12 minutes before it starts loosing power. If I drop down to 2300-2500 rpms for a few minutes I can go WOT again. I rebuilt the carb and thinking I had a float or pump issue but that did not solve the problem, I changed the fuel filter, and checked fuel pressure. I am getting 15psi. I am sure I am missing something quit obvious. If you can point me in the right direction that would be great. Thank you Kevin.

 

[alldodge]

I have a 96 350 with a mercarb 2 barrel. The issue is when i run at WOT I can only run for 7-12 minutes before it starts loosing power. If I drop down to 2300-2500 rpms for a few minutes I can go WOT again. I rebuilt the carb and thinking I had a float or pump issue but that did not solve the problem, I changed the fuel filter, and checked fuel pressure. I am getting 15psi. I am sure I am missing something quit obvious. If you can point me in the right direction that would be great. Thank you Kevin.

If your getting 15psi, that is way to high for a carb engine. Now if you meant 5psi then that's fine.

I would start with the anti-siphon valve at the tank, it looks like a barbed fitting but has a spring loaded check ball in it. Have you changed the fuel filter? Also check the fuel tank pickup tube for a restriction, if anything else run the motor by using a 5 gallon gas can. Have you left the fuel pressure gauge on the engine while it was running?

 

[trainwrecker22]

It is 5psi not 15 as auto correct thought I wanted to say. This anti siphon valve where is it located? Would this be the cause of when I fuel the boat I blast fuel out the vent now too? I was fueling it back up and the pump did not shut off but started blasting out of the vent. That is new this season

 

[alldodge]

It is 5psi not 15 as auto correct thought I wanted to say. This anti siphon valve where is it located?

It is attached to the tank outlet. It looks like this

It has a check ball inside it that is spring loaded. If it gets clogged up the pump will have a hard time sucking fuel out of the tank.

Would this be the cause of when I fuel the boat I blast fuel out the vent now too? I was fueling it back up and the pump did not shut off but started blasting out of the vent. That is new this season

No, the anti-siphon valve has nothing to do with filling. Fuel blasting out the vent tells you it is working, just put something over it to catch the fuel when your refueling and do it slower