Sounds very similar to my leak. Won't leak on the hose, only in the water. Definitely leaks more the higher the rpms. Just putting around I barely get a drop.

Just trying to wrap my head around something here. Everyone else's bilge is bone dry other than the OP and member in post # 11?

ck the cooling hose connection on the housing, have seen them corrode, sometimes the housing is beyond repair as well, tuff with engine in, might try one of the remote camera's with flexable head to look where you can't...

Speedo hose?

you know, that's probably the one thing I have not tried to look at. Speedo is in the process of being disconnected anyway in favor of a rather inexpensive Faria GPS unit. Where ever the leak is coming from, it seems to have a little pressure behind (sprays) it because it leaves droplets over a fairly large area.

Steering pin worn out and leaking? Mine was letting in a lot of water until I got it replaced.

Speedo hoses very small and up fairly High where it comes through the transom. Yours sounds like a larger leak down lower. More than likely either the y-pipe itself, or between the transom assembly and the hull.

Outdrive is off. Boot, bone dry inside. Speedo, no leak, steering arm no leak, (leaks before water gets that high), sea water intake hose sound no rots, could be at he 45deg, connection in the transom plate, but I can feel it from inside, seems ok, hose tight. Water drip from hose at high volume in and around the gimble, and shoving the hose up as high as it goes, lot of water, drip inside bilge bellow driveshaft.
I might have to remove the gimble and the boot housing, but not sure how. Will research it a bit.

I had a Alpha that was leaking in the same spot (right under the driveshaft) that turned out to be the trim ram distribution plate seals. The water was coming from the area where the Y pipe went. Very easy fix from the outside.

Now, while the drive is off,, drive to the boat ramp and fire up the hose. Back it down the ramp and start filling the bilge. Wherever the water leaks in, it will run out. Either thru exhaust-engine comes out-or around edge of transom assy-might get lucky sealing it but probly not, or trim hose manifold-buy a gasket...don't fill it to the gimbal bearing or the starter. But it'll probly start running out as soon as you have 3 inches of water against the transom.