50 hp hesitating

[dbruce85]

Purchased a 50 hp 4 stroke EFI Big Foot for my 18ft Pontoon Boat. It starts on a dime, runs quiet and smooth. Tops out at 5500/5600 rpm, 18mph with an 11 pitch prop. Unless I really accelerate slowly thru the rpm range it will stop at 4000/4500 rpm and hesitate, feels like it's trying to take off but doesn't. If I throttle back down and baby the throttle it runs back up to full throttle.
Any ideas what it might be?

 

[AllDodge]

Sounds like a fuel supply issue
Have you tried to pump up the bulb and see if that allows it to go on up in rpm?

 

[dbruce85]

I pumped the bulb before I started out, did you mean to pump it while it was hesitating.

 

[AllDodge]

I pumped the bulb before I started out, did you mean to pump it while it was hesitating.

Yes, like to find out if it's the fuel pump or a restriction

 

[dbruce85]

Throttled up fast, hesitated and sat at about 4000, the 1st pump of the bulb it was soft, next pump it was firm again but it didn't seem to help the motor. Throttled down and Throttled up slow and it ran to 5500

 

[AllDodge]

It's not the pump
Next thought is carb clogged up some. Appears to have plenty of spark because once up to rpm it doesn't miss

 

[dbruce85]

It's fuel injected, every time I slowly throttle up it goes to full throtle. If I throttle up quicker about 3 out of 4 times it starts to hesitate at 4000 or so.

 

[AllDodge]

Scan for codes and check fuel pressure

 

[dbruce85]

OK, ends up it was spark plugs. They were changed now even if I throttle up fast it reaches full rpm and runs great