Have Boat Questions? Ask a Boat Repair Expert.
Are you familiar with how these engines operate? They are mostly computer controlled. Do you have the SystemsCheck gauge? Do you have the cabling and software to run the computer diagnosis and check for trouble codes?
Do you have the fuel pressure gauges?
Have you tried to keep the engine primed with the primer bulb?
Does the engine start right back up or does it take a while?
Ok so you throttle back then it runs ok for how long at what rpm? Then when you go to give it throttle it stumbles, correct?
Have you pulled the spark plugs?
Sounds like there is a restriction in the fuel delivery. You need to get hold of some fuel injection pressure gauges, run the engine, and see if the fuel pressure is sustained. You are probably running out of fuel.
I would also recommend using a remote tank to see if it is the boats fuel system or the engine. Just run the engine on a 6 gallon tank.
If it runs correctly then the hose is collapsing internally, the anti-siphon valve is restricting flow or another restriction.
Try this and post back what you find.