Merc 32-865277A02 Oil drain kit plug thread specs
 

This hose kit is already on the pan but will not fit through the transom…I need an adapter from my oil extraction pump’s 3/4” garden hose female attachment to the end of this hose kit…hose kit has the plug termination. So I need a brass adapter from 3/4” ght to */* npt (?)…anybody know?

Drained a pair today. It’s small. I’d guess 1/4” npt. Maybe even 1/8”npt. A 11mm (7/16”) wrench took it off.

Do you think that any fitting that would replace that plug would be too small/restrictive for an electric pump to work…is a guy better off to cut off the end assembly and just screw clamp a barbed fitting on the hose?

Pretty sure they are 1/4" NPT. Mine is 225 miles away.
Ran across THESE on Ebay, then you could run an NPT close nipple between the drain hose and the linked adapter or even a short hose with 1/4" male NPT on each end.
At any rate no matter how you rig anything up, I myself would never cut the crimped connector/plug setup off the Mercruiser hose.
I'd "hack" a rigged setup somehow else.
I use a vacuum oil extractor on the same hose and I use an NPT to pushlock connector to attach to my extractors 10mm tube and it draws fine.

How come it won't fit through the transom drain plug hole?? The standard oil drain kits are designed to fit through most standard transom drain plug holes.

It would fit through the hole but there is a fiberglassed support piece inside that reduces the approach angle.

I would just shove a 2' section of more flexible vinyl tubing through the drain plug that you can temporarily press onto the end of the drain hose each time you change the oil.

I have to pull the plug rings off to get the hose to come out, then seal them back in place when finished

The threaded brass ring with three screws into the transom?

yes.......the angle is all wrong and wont let the bulky end to make the bend