I finally determined that the water slowly accumulating in my bilge was from leaky joints hidden under the forward shower control. I am having trouble getting the top off in order to access the valves. I removed the set screw and the lever shown in the photo and I expected the top to lift off. I have spayed vinegar and been quite aggressive with it but it hasn’t budged. I wanted to know if there is a trick to removing this before I break it.