Hi Dian,
You can indeed get your boat registered with out being physically present or taking your boat there. Guinea-Bissau is a very good option, you need to apply over the internet and your plates and registration document will be delivered direct from Guinea-Bissau by DHL within a few weeks. The plates can also be picked up at the Guinea-Bissau consulate.
If you need any further help, you can get in touch with us.We specialize in
offering tax free boat and car registration services to our clientele most based in Europe. We have helped diplomats and businessmen in getting their cars and boats registered