Not much information on that control....
Are you sure that is for an I/O
It may be for a inboard style boat and the neutral
Ok, so preliminary findings so far:
Drained the lower unit gear oil. No water, but old oil for sure.
Ran compression test and
Pull the ten pin connector apart on the engine and inspect it. It is the large plug with a hose clamp on it.
Ok guys there has.been some breakthroughs. I drained the foot and the first stuff to come out was slightly thick like oil brown stuff. Looked like exactly