If your speedo stops working, it's a known issue. With boat on trailer raise trim all the way up. Look under backside of out drive for a loose black hose. This is the pickup hose for the speedo. It should attach to a barbed white plastic fitting that will appear on the out drive as a square white piece. These get brittle and the barb end snaps off. I wish someone would design a replacement part made out of better materials. I've attached image of Volvo Penta part below. Use dental pick and vacuum to get the plastic pieces out of your intake,. Hardest part is removing the barb from the tube. You can likely crush it into pieces with needle nose pliers and remove the pieces. See,
