27zr thru hull seacock
 

I am a newbie to the forum and to big block engine boating. Just purchased my first Donzi (2009 27ZR). What is the thru hull seacock for. Looks like the fresh/raw water enters the pump thru the sterndrive. Can't figure out what this is for. The ball valve is in the open configuration.
Having a constant buzzer but this has happen only 3 times. I boat on a fresh water lake but the boat was salt water prior. Each time this has happened we anchored close to the shore. I have flushed the system. Taken the hoses off the oilcoller and flushed it. No debris noted. I can't figure out how to get to the impeller to check it.
Thanks for any help.
TIm

Not 100 percent sure on the 27 but other ZR's in the lineup have a through hull for air pressure relief. You basically leave it open and it does what it needs to.

The water pump should be at the bottom of the engine. Remove the serpentine belt, then pull the whole pump off, after you get it out of the boat you can change it on the bench. And yes, it is far more of a pain in the azzz than it should be for a wear part.

Thanks for the fast reply and help. I was looking at the water pump and it looks like I need to remove the fuel pump/filter assembly as well. Even if I remove the belt etc it doesn't look like there is any way to get to the bolts or get the assemble out. There isn't any space between the engine and the back seat. Is it safe to remove the fuel pump assembly?
Thanks again.