HD,
As you're facing forward, check the lower part of the motor on the right side. On the block,close to the pan there's a poppet valve that controls water pressure through the block. There's a small hole in the larger diameter portion of the cover that will leak water if the diaphram inside gets a tear. Due to the long time the boat sat, that diaphram may have broken when you started it up. Very easy to replace with an available diaphram kit. Also suggest you go all around once more and tighted all the nuts then run it with the hose attachment and check it out.
Let me know how it goes.
Ron