Deck waste fitting, thread size?

[testlab]

I have a 1996 330DA, does anyone know the size and thread type for the waste outlet. I need to purchase a pump out adapter and I have a choice of a 1-1/4" or 1-1/2" BSP and not sure which one will fit. If it's something else I will have to make it. Any help appreciated.

Thanks
Dave.

 

[Old Vet]

pretty sure it's 1 1/2"

 

[Lazy Daze]

And, I be surprised if it was BSP (but maybe if the boat was made overseas?). This is what I would normally expect to see used: http://www.northeastsanitation.com/...343502&Category_Code=Holding_Tank_Accessories