Looks like the Moyer Catalina style exhaust (if that's the one you're looking at) has NPT threads on the output of the black water mixer section.
https://moyermarine.com/product/exha...exht_01-0_562/
If true you could extend it by a foot with a piece of black iron pipe.
You'd need to check your hose would go over the OD of the pipe, but that is also true for the exhaust assembly un-modified.
I suppose there could be a corrosion concern with black iron after the mixer but easy to change every few years.
Note that the separate brass water mixer from Moyer does not have NPT on both ends like the black one in the link above appears to. It has NPT on one end and a hose barb on the other - I fitted one last year.
https://moyermarine.com/product/inli...exht_01-1_324/
Good luck
Simon