I main Yorick and I will tell you exactly how to beat him. ALL IN. That's about all there is to it, you can all in any Manamune Yorick all day, their damage is just too low for all but poke champs. Don't wait for him to get farmed and ready, just wait till he tries to poke you from afar and gap close on him and kill him, he'll hit you for roughly 250 damage max then only be able to auto you for 70 a pop every nearly 2 seconds. Use that to your advantage. You can do this until he's built armor or a good amount of damage.
If he builds early damage (starts Long Sword) don't do that because he is gonna hit harder, and his ghouls are gonna hit harder, and he's less likely to poke with his heal from afar because he'd rather take an auto trade then cast the Heal and auto trade again (you will probably lose that fight unless you have a stun to negate his second auto). I don't know what champ you played against him but if it's a poke champ you probably lose, if it's a tank, probably not that good either, if it's a fighter you should be able to win since they generally have a better all in than Yorick now days. Also, if he does hit you with ghouls hop in a bush to deaggro the ghouls and run at him from the bushes to trade some damage avoiding getting hit by the healing ghoul.
Counters to Yorick include, Renekton, Xin, Riven, Jax, basically any all in champ that does high burst with a stun.