Suzuki and Yamaha do 100:1 up to 30hp. 50:1 is the ratio for Mercury Mariner
However the OP said his OB was rebuilt. Depending on the rebuild he may want to rebed the engine on a mix of 25:1 for 4 - 8 hours and change plugs after he's done. They will foul.
Best keel might be a lIfting keel on a southerly 47 or suchlike if budget permitsHey, just In the process of buying a boat and will likely be going for bilge keel. Do you ever wish you had a different keel?
enjoy your trip