I have a hummingbird model 787c2 fish finder I am getting ready to mount on a new boat, took transducer off old boat and it looks like something is or was leaking from transducer, looks like black tar but is not sticky, I have two other boats that is set up for this fish finder and check their transducers and all three of them looks the same way...any help? I have not used either of the other boats in about 2 years, can anyone tell me how I can check to see if they are bad?
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