I bought a 1993 Sprint 255 from a buddy & he installed a Humminbird 525 depth finder. It doesn't read right. If your sitting still it reads right sometimes & all of a suddun it goes to reading 0.9 ft. When moving on plane it's right everytime. My??? is how do I measure dead rise so I can remount the transom style transducer to humminbird specs??? I saw on another post that if more or less or equal to 15* deadrise that you mount them different. Thanks
