speedometer reading zero
 

clog in small hole at leading edge of bottom of outdrive.
inch or two above prop shaft
I thought at first it was a chip in case, but was clogged hole
work out stuff with stiff wire
depth is about a standard drill bit deep
speedometer seems to show 40 with about 40 lbs pressure
perfect tool is 30 # freon bottle with air hose and
blowgun with a rubber tip
pull loose tubing inside held with a wire tie in dead center behind motor small brass fitting
attach some tubing here to blow out outdrive section
apply air to tube to test speedometer
cleared hole, speedo works
I just floated in water with boat lifted above water while rodding out
mariah sx19 03 mercruiser alpha