https://youtu.be/QEL4THMZlZA
That link with show you how to clear the clogged speedo pickup tube on the front of your outdrive. Use a small 1/8 drill bit and rolling it in between your fingers ( don't use a drill). The bit will work through the wood or mud or what ever debris you got trapped in the hole. This is generally the problem with alpha and brovo outdrives