03 johnson 115 sputtering

[wis2ohio]

I have an 03johnson 114 4 stroke the motor ran great when you first start off and half throttle however when it's wide open the boat starts to spit and sputter but never stops running the boat will then take off again until it seems like it's loosing gas then stop again and take off. I have removed the vapor separator and the screen is clean and the needle is moving freely.
the fuel lines do have some build up on them so i'm not sure if those need replaced but i will probably replace them.

Anyone have any ideas what could be wrong? I was thinking maybe the fuel pump inside the vapor separator might be bad but not sure how to check that

 

[Skylar.Hale]

Check the fuel pump for any rips / tears in the diaphragm. Also check fuel pressure with an inline pressure gauge at WOT IN THE WATER NOT ON MUFFS. You will need full load on the motor and muffs just don't cut it.

 

[wis2ohio]

Check the fuel pump for any rips / tears in the diaphragm. Also check fuel pressure with an inline pressure gauge at WOT IN THE WATER NOT ON MUFFS. You will need full load on the motor and muffs just don't cut it.

Thanks for the reply.
i didn’t notice anything wrong with the fuel pump and it seemed to operate when the key was turned on.
For the inline fuel gauge where exactly would you do this? I’m new to this

 

[Marko101]

Good idea is to temporary install clear fuel hose to see if your fuel system is pulling in some air. Do you se portable or internal gas tank ?

 

[wis2ohio]

Good idea is to temporary install clear fuel hose to see if your fuel system is pulling in some air. Do you se portable or internal gas tank ?

Internal fuel tank