Digital Speedometer Question

[micfia66]

I recently had water in my Digital Speedometer. The Yami service guy at the marina told me it was salt water and not rain water from a weak diaphragm in the speedo where water pushes against from the engine to create pressure which registers as MPH? This speedometer has a small black tube attached to the back with a plastic tie. No one I spoke to has ever heard of this. Is this true? and can this be fixed or do I need to replace it. I have a 175 HPDI on a Grady. Your advise would be appreciated. Thank you.

[boats.net]

I don't know of any where to get it repaired, would need to replace it.