Originally Posted by SeaSkills
There's a good chance that fitting a magnetic compass into a small console with loads of electronics around will give you a fair amount of deviation. Unless you particularly want to play with "old-fashioned" navigation, or you want to have an option that doesn't need a power source - have you thought about a fluxgate compass?
I thought I would have problems with the electronics, but there is no discernable movement of the compass when I switch on all my electronics. (see pic) I've added a Garmin 550 plotter between the black label and the sounder since the picture was taken and still no problem.
The compass is American and specially made for powerboats, so it's very dead beat (compass-ese for steady). I bought it locally, but lost the box so can't remember the make. It has compensation magnets and I'm very pleased with it. A quick Google showed Ritchie has something similar.
Important that you get one for powerboat use. Others are not steady enough.
PS I made the wooden bit of the binnacle so the compass mounted level (but didn't get it quite right )