The speedometer tested good with low air pressure test. Tested the air hose from the speedometer to the lower unit connection...no blockage. The down tube in the LU appears to be plugged with debris. I used 100 PSI compressed air and only a wisp of air and a few drops of water came out of the small hole on the front of the LU gearbox case. Any idea to clean out the air/water pressure passage besides dropping the lower unit? Thanks.