1989 Evinrude 50hp trim pump noise

[bassfearmee]

Hi, my trim pump on my 89 Evinrude 50hp works fine but makes a screeching noise when lowering the motor. When raising the motor, it sounds good, but coming down is the problem. I've topped off, raised/lowered 5 times, topped, raised lowered and no change. I noticed that when I open the fill plug, there's a lot of pressure in there, like air and fluid sprays out. Is this normal? I'm wondering if there's a bad relief valve or something.

Thanks,

Bob