[macojoe]

well compass use magnets, and any metal that is near it will tghrow it off a little.
This includes speakers, stereo or VHF radio speakers.

You have a window su[port right above it. Will it be alot ??

You can have a boat yard or follow the instructions to adjust and you will be fine.

of corse you need a none working compass to set yours.

It all depends ow accurate you want it to be?