Discovered water in Saildrive this morning. Assuming it's the seal, although I hope the casing is not breached.

https://drive.google.com/open?id=0B7GvyOr-FTQYOUg2VUx4dDZzMUk

Yes, hope your right about it being a seal.
I hope it does'nt have anything to do with the fact that a diver cleaned the running gear on Friday.

keensailor said..
Discovered water in Saildrive this morning. Assuming it's the seal, although I hope the casing is not breached.

https://drive.google.com/open?id=0B7GvyOr-FTQYOUg2VUx4dDZzMUk

Think there might be a bit of confusion here on saildrive leg water seals. The complete saildrive leg is sealed with a membrane between the leg and hull to keep the sea outside. This is usually a double membrane with a water detection alarm between to indicate when water has breached the outer membrane. This appears to have occurred in your situation. I suspect that you are actually removing the alarm sensor in video.
There is also a gearbox oil seal at the prop shaft which prevents oil leaking from the shaft (and water leaking into the gearbox. Clearly this is not the case in your situation as you would see milky oil on the dipstick which is located top of gearbox and will be a screw seal.
It is usually recommended to change the membrane after 7 years service.

The saildrive boot came loose and I removed it some months back. I wonder whether that has put more pressure on the seal. The boot is not meant to be water tight so I don't see why not having one would cause the issue.

I'm no saildrive expert but FWIW, oil and diesel will only dislodge water as they don't mix, right, so wouldn't metho which does mix with water and then evaporate be more suitable? As I said.... Just thinking?

Also, you've probably already done this but can you put it in neutral while the oil or whatever is in there and turn it by hand to dislodge any trapped water?

As I said I m no expert so ignore this if I'm wrong.

Good to see you found the issue.

Hopefully its easily sorted.

I live in fear of fishing line around the prop.

Some way irrationally. ...so its good to have some support for when I go crazy about lines around the prop and carried on like a crazy freak making sure it is always completely cleared.

P.s 30 years out those seals...wow