old mariner/Yamaha 15hp outboard carb

[mrmike]

Can anyone help I am trying to track down a replacement carb for this mariner engine
serial 684c -s - 071779
the carb it has atm is a 6E773 9H which has a venturi bore of 15mm

I have swapped out the 4 reed block for a 6 reed block and am now after a replacement carb with 19.5mm venturi bore ie 15hp carb not 9.9hp

all i can find on yamaha parts list is 6e770 = 9.9n and 6e870 = 15n

does any one have any idea what carb part number I need or would any with 6E8 fit

Thanks
Mike