Mercury Flush adapter adapters...
 

I have a couple of (new to me) 2007 Optimax 225s that came with fresh water flushing adapters installed next to the pee hole on the lower backside just below the removeable cowling.
I BELIEVE I have these:
I believe the male part of the current adapter has a check valve to keep the water from flowing out while the motor is running normally in the water YES/NO?
Is the check valve "defeated" when the female quick-connect adapter is installed YES/NO?
Anyway, with the boat on my lift, I have a hard/impossible time getting to the adapter with a garden hose (without getting into the water). What (I think) I'd like to do is add about 2-3 feet of (black) garden hose to the push-on coupler and zip-tie the female end of the garden hose to a suitable spot at the back of the boat so that I could simply attach the garden hose from inside the center console boat.
My concern is if the 3 foot extension is left installed while I boat, will water be push out of the hose (or is there some sort of check valve to prevent this).
Thanks,
Tom

Why couldn't you just put a cap on the end of the 3 ft hose ? Take it off when you hook up your water hose to flush.

No need to spend $30 on that fitting, just screw your flush hose into the outside fitting on the lower cowl. There is a brass check valve on the engine where that hose feeds. When the engines are running no water escapes at that connection, it is a one way in kind of thing. Remove the top cowl and trace the lines, you’ll see what I am referencing. Pull up the schematic on Boats.net and you can see it.

That would work too, Thanks!

I have not seen/noticed this fitting...I will look at schematic on Boats.net.
Thanks!