1993 Yamaha 25hp MSHR, bogging down?

[duckhunter11]

I have a 1993 Yamaha MSHR 25hp outboard motor (2 stroke). Recently it has started "bogging down" about a minute after reaching 3/4 to full throttle. Once it has "bogged down" from full throttle it will only move very slowly no matter where the throttle is. I am able to disconnect the fuel line and let the motor run out of fuel, once the line is reconnected the motor will run fine until 3/4 throttle is run for a continuous minute. Runs fine on the hose in the yard. I have changed spark plugs, fuel filter to no avail. Any information or suggestions would be greatly appreciated.

Thank You!

Peter

[robert graham]

Sounds like a fuel delivery problem, weak or bad fuel pump diaphragm, closed or plugged fuel tank vent, some restriction in fuel lines above 3/4 throttle flow rate..