50 hp 4 stroke efi Mercury only low speed

[kenreed]

I just bought a used Tracker boat with a 50 horse power Mercury outboard. The boat and motor have been used very little since 2003. The motor will start perfectly. When we launched it, the boat ran smooth and got up on plane very nicely. We killed the motor to try the trillong motor. Restarted the outboard and headed back. After getting on plane and running a few minutes at 3/4 throttle, the motor started slowing down and then died. I restarted it, but it would only stay running at about 1/8 throttle. I removed the fuel pump and the gaskets and diaphram are good. I checked the fuel and replaced it. I checked the fuel filters and they were new. Any ideas?

[boats.net]

Would need to run fuel vacumn and fuel pressure test to see if have a fuel restriction in fuel delivery lines going to engine and enough fuel pressure to injectors.

[JUST-IN-TIME]

VST filter is probably clogged, see it daily at my shop