In 867 you already had to wait around 30 years to get boat technology, doesn't that mean that in 769 you'd have to wait 100+ years?
Use trick to switch to republic to have instant boats?
Then wait 10/0 years or inherit some lands from other Christians.But as a republic you can't ever change capital, and I don't intend Socotra to ever be my capital.
Just... research Ship Building tech with tech points from your Spymaster? Then you just have to save up about 75 gold, build a ship builder, wait for the galley levies to replenish (use your marshal to speed it up), and raid some Muslims with your boats. I did this in Ireland in less than 10 years.