We were running north through Martha's Vineyard sound a few weeks ago. We were buddy boating decided to go 'inside' between the lee shore and a long shoal that runs North/South for about 8 miles. It's a fairly narrow area, relatively. We were about 1/4 mile from the shoal and about 1/2 mile from the lee shore.
My auto-pilot suddenly take a 90 turn to port. I hit Standby and get back on course. I reset the AP and things appear fine, then about 5 min. later another 90 turn to port. This is sending us straight for the shoal. Again, I reset AP and things seem fine. 3rd time is a 90 degree to Stbd. OK, I 've had it. I turn off AP and start hand steering.
While hand steering I mention to my wife that the steering feels oddly 'loose', but I have steerage so don't think much of it. After about 5 min. %^$#@!
I pickup the VHF and hail the boat in our convoy directly behind me. (We all agreed to monitor the same channel so I know everyone else can hear the exchange). "Be advised, I'm coming to a stop". the response "Uh, ok......is everrything OK?". I respond "I've lost steerage".
At this point my wife looks up from her book and says "Uh, did you just say that we lost steerage??!!!!"
I run to the lower helm where there is still some, albeit sloppy steerage. I have my wife take the wheel and hold a position using the lower helm. This is normally a 6 turn wheel (lock to lock). She advised afterwards she was getting 10-12 turns lock to lock just to hold position in idle.
I pull the hatch above the steering ram.....I immediately seem hydraulic fluid EVERYWHERE. @#$%$#%!!
I'm looking around and I see no burst or detached hoses. The steering pump looks fine. then I look at the AP pump. It's covered in steering fluid. I put my hand on the closest fitting......it spins in my fingers FW#$@#$#!!
I start tightening and it's just spinning and spinning. After some perseverance it finally seats. I run and grab a wrench and tighten every single hydraulic fitting I see. This is the only one with an issue.
I go into the engine compartment and grab a steering bleeder and a bottle of hydraulic steering fluid. I run to the upper helm and re-fill the system. I check the steering and AP pumps again and no leaks. We manage to continue on our destination.
As I'm pulling into Vineyard Haven the steering starts getting loose again. If I spin the wheel vigorously 3 turns port, 3 turns Stbd i can feel pressure build up again, so I realize what is occurring.
In my panic, I filled the system, but didn't bleed the system. Air bubble were working their way up through the system to the top, which happens to be the upper helm. The more I steered, the more air bubbles bled up and the more I would loose steering in the upper. By vigorously turning the wheel, I was effectively aerating the oil giving me enough fluid to steer. I limped through the anchorage and managed to find a spot.
The challenge was, my wife was in the Whaler we were towing. I was alone. I had to drop the anchor myself and the only helm that has a windlass control was in the upper.
Once anchored I bled the air out of the system including the AP pump and everything was back to normal.