70HP Beto 6H3 Yamaha Question

[Binduss]

Hi,
I was wondering if anyone could help me identify what this bolt is/does in the picture I have included with the red arrow pointing to it?
I am currently servicing the motor (this pic I found on the net) and this bolt has me stumped.

 

[99yam40]

I think it is a plug you can remove and install a water pressure or maybe a temperature sensor

 

[Binduss]

That makes sense!
Cheers 99yam40.