81 Johnson 50hp 2cyl. Last week got fishing line in prop had to replace both seals. Took boat out running in open water boat quits restarts fine. wont go much over a idle. Replaced fuel pump. When in the water under load about mid to high speed makes a screach noise locks up? will restart runs good with no load. Give it some load makes screach noise and acts like it lock up the motor the noise comes from lower unit I think? any Help