Lower unit question

[<pinehawker>]

on my lower unit there is a small hole that faces the boat. it appears there is small pieces of string that come out of this hole can you tell me what it may be.

[<boats.net>]

There is speedometer pickup built in the gearcase of some models and it probably has grass in it

[<pinehawker>]

can i just pull the grass out, i figured that was what the hole is in the lower gear box but wasn't sure. Wanted to check with someone first. Is there also another was i can make sure i have the hole cleared out, can i push something into the hole or not. Thanks for the help