Yamaha F75 TLRC Vacuum port fitting size?

[Timmstng67]

Hi,
Can anybody help me with the size of the fitting that you install to hook up a carburetor balancing tool on a Yamaha F75TLRC. I have found two sizes
5MM and 6MM any help is appreciated.
Thanks Tim

[boats.net]

They are 6mm on the F75 engine.