When I cabled my second depth finder it was from the floor of the bathroom to the flybridge. It was purely a stand alone backup depth finder. I took the shelf out under the sink and the medicine cabinet out. Go to the cabinet closest to the helm in the stateroom on the starboard side of the boat and take out the small section in the forward area of the cabinet. All of these are a few screws each.
Back in the bathroom, you can work the cable from the floor, up the wall to behind the medicine cabinet. There are two chases (basically plastic downspouts you would see on a house. Use an electrician's snake from the stateroom end and fish it to the bathroom, tape the cable to it securily and with someone feeding from the bathroom, pull it back to the stateroom. You can get a cheap electrician's snake from Home Depot.
Then feed the cable from the stateroom to the main electrical area under the lower helm. In the electrical area there are couple more chases that go up to the flybridge area. It seems to me they were very full making it a bit more difficult but run the cable through them to the flybridge. Pull from the flybridge end. I put the depth finder near the E80 which took just about all of the 30 foot cable that came with the depth finder.
There is a power block under the flybridge dash area so the power can come from up there.
2006 34' Hull #81