I have a 2002 225 EFI Mercury. My speedo has NEVER worked correct since new. Here is the mystery. The hole in the lower unit could be completely clean and WOT shows maybe 30 mph on analog gauge. When the hole plugs completely with wood, the speedo reads slightly higher. It seems there is somehow a passage between low water pickup and pitot tube. Even when brand new I could blow air into pitot hole and could hear air coming out low water pickup area. I have just not worried about it for the past 6 years or so but would be nice to see it work. Analog gauges are usually optimistic at anything over 60 . Any ideas on how to fix this? I have had lower unit off and did not really know what to do. I have checked gauge from LU forward and seems to respond correctly. Could the hole coming in from the top into pitot tube be thru? Can pitot tube be replaced?