How can I make a boat route to a far away island?

How can I make a boat route to a far away island? (from Kavala/Greece to Mytilini) ?
When I zoom out to have both places in screen I am not allowed to edit the map. I have to zoom much more and Mytilini is not visible.
I tried with iD and JOSM.

Thank you!

I think it is not possible with iD, but with JOSM you can download many (smaller) areas, so that in the end you have the whole area.
You can also try the mirror download, which is faster. But you need an extra plugin for this.

indeed! … please try the offline editor JOSM to edit larger areas or objects. After some days of learning, JOSM is not hard to use. Try it.

see http://wiki.openstreetmap.org/wiki/JOSM

Thank you for replies!
I will try with mirror download.

stephan75, I already use JOSM, but yet not for everything. At the time I do some things with iD and some with JOSM.

I tried that with JOSM and mirror download, but I have problems:
-My PC becomes very sluggish when I load this bigger part to be able to see both places.
-The names of cities, villages, boroughs etc become so dense that I can not see where the harbors are. Is there a way to make the names not visible?

Thank you

You can try using http://overpass-turbo.eu/ and select coastlines only. This will minimise the downloaded data and you may be able to get all coastlines concerned. Then export this to Josm. Finally in Josm load fully the areas around each of the two end points of your route so you can locate the docks properly.

You may, though I have not tried for such a long distance or over ocean areas, draw and save a gpx track in a program like gpsies, then open in josm and right-click on track in the layers box, and download within say less than 50m of the track.
You should then be able to add your route.

Thank you for both answers!! I did it with overpass-turbo.
Are my tags correct?
route=ferry
foot=yes
motor_vehicle=yes
name=…
name:en=…
Should I add a relation? (What exactly?) I think I should not.

In port of Peraeus all routes are tagged this way:
waterway=seaway
no other tag
and there are 2 relations for each, eg:
Piraeus-Salamina
Salamina-Piraeus

Are these correct? The tag seems wrong to me.

Thank you again!

Well, I am not sure, but maybe you can get more detailed information and feedback in the http://wiki.openstreetmap.org/wiki/OpenSeaMap universum …