1976 Gulfstar 36 MarkII water plumbing size

[Billylll]

My Gulfstar 36 Mark II has all copper hoses and fittings in the freshwater system. Can anyone tell me which size piping is used in the fresh water system? I need to replace the freshwater pump with a new Jabsco VFLOW 5.0 and the copper looks smaller than the smallest sized adapters that came with the new freshwater pump. Does anyone have any ideas how to install the new freshwater pump on the old Copper lines? The boat is 120 miles away and I want to fix the freshwater system before I take the boat on it's trip to Little Egg, NJ. from the Middle River, Maryland.
Any help or ideas would be appreciated.
Thanks,
Bill

 

[On The Rocks]

Mine was 3/8. There was a brass fitting 3/8 to 1/2 where it connected to the pump. I've pulled it all out and replaced with 1/2" PEX. Much better water flow ?