Outboard trouble

turkeyman

I have a 75hp mercury 99 model.  I used it approx 3 weeks ago.  It would not get up on plane.  I thought the carbs might be clogged. I put a can of sea foam in the gas, ran the boat over the last couple weeks on the ears not in the lake. Last Friday I went out to crank it up again to make sure it was running before I took it out saturday. It would crank but shut right back off. I decide to take all 3 carbs off and clean them, after cleaning and putting them back on the motor I have the same problem. I then change all my fuel lines, the bulb and check fuel pump I still have the same problem. While changing the lines I took the line off after the fuel pump and started the motor. It will run all the gas out of the carbs but as soon as I put the hose back on it stalls out.  Do you think the sea foam made things worse? 
Any suggestions will be appreciated.
Thank you

larrywitt

Air vent may be plugged so it is starving for fuel.

turkeyman

Thank you did not consider that. 

MelbourneMark

I've seen the back-flow fitting in the fuel tank get clogged and produce similar results.. You can replace the fitting itself, or remove the piece in the ****. (It won't prevent backflow then)

also, a clogged/dirty fuel pick up tube in the tank will do similar results. 

If if you run the motor on an external tank; this can narrow down your issues. 

Alex from GA

Agree with Mark, run it on another tank.  

turkeyman

Thanks to everyone I will let you know what happens.

craSSh

Sea foam will loosen up the carbon and can foul your plugs. Check your plugs, they might need to be cleaned

turkeyman

To everyone, thank you for all the input on this issue.  I rebuilt the fuel pump and it is running fine now.  I didn't think it was the fuel pump it seemed to be working.  Maybe not enough pressure, not sure about that one.  However it is running good, hitting the flats in the morning.   Thanks again