It better not be brass or you are in serious trouble ! Brass is never used below the waterline (except by French builders) because it de-zincifies in salt water
and literally disolves after 5-10 years.
It is impossible to tell the condition of the metal from this photo
due to blue/green deposits which are a result of corrosion
. This is often just a surface condition (but not always) depending on the quality of the "bronze". The hose is toast and the clamps are severly corroded. If you try a use the grease nipple it may be so corroded that it breaks.
You have a dangerous condition. Do NOT play with this, bite the bullet and pay a qualified technician to inspect.
PS. Previous references
are incorrect. What you see is "galvanic corrosion". Electrolysis
refers to a chemical change in an electrolyte with the passage
of electrical current
and has nothing to do with corrosion
on boats. Be wary of advice from anyone who uses this term in reference to corrosion.