Tracker by Mercury 25 hp 2000 year model, won't run full speed

[jaybee]

Engine will only run up to about 1/4 speed. Cranks and idles good. When it first started it would open up and run for a while then start slowing down to 1/4 speed. Now it won't go past 1/4 speed. Have clean gas and clean filter.

 

[racerone]

Have you checked / replaced waterpump impeller ??-----------Checked for ruptured diaphragm in fuel pump???---------------Good strong spark on both cylinders ?----------------Time to do a compression test as well.