What is the little hole in the leading edge of the lower unit? DF140

[johncha]

I've noticed a small hole in the front edge of the lower unit. At first I thought I must have hit something at speed which chipped the casting, but on closer inspection it looks like it's meant to be there!
Very small traces of oil leak out of it when the boat is stationary. I'm just curious to find out what it is. If anyone knows what this hole is then I'd be very grateful for any information.
Thanks, John
suzuki hole (2).jpg

[tsturm]

water pressure pick up ( aka speedometer pick up ) for a prehistoric speedo.

[johncha]

Thank you for the reply tsturm, that makes sense.
What a great source of information this forum is