Yamaha 70 1997

by Cliff
(New Zealand)

I can go at full throttle for about 30 seconds, then the engine slows down and has no power. If I stop the engine for a minute, then start again, I can have full power till about half throttle, and the engine will maintain power at half throttle. It has plenty of water flowing out the tell tale. Oil tank is full. No alarm sounds. Could this be a fuel pump issue, or a blocked fuel filter (if it has one)?