Last week I was involved in a salvage operation.   A 30 foot twin outdrive sunk at her mooring in a short span of time.  It was observed floating normally at 0600 and by 0930 she was on the bottom.   Fortunately the bow was still above the water and I was able to get a line on the stem fitting should it go completely to the bottom.  The next job was to don the scuba gear and take a couple of lift lines down to the aft cleats.   These were mounted in a semi virtual orientation so I could rely of shear strength for the lift. 

After positioning a floating platform near the bow we moved a powered catamaran with two chain hoists over the back of the boat.    Slowly we raised the back of the boat until she was again horizontal about two feet below the surface.

When we approached the shore we grounded in about 4 feet of water.   Using a long rope a block and a ¾ ton pickup we slowly worked it into shallower water.   When the water was below the walk thru transom door we started the pump until she was once again afloat.

Bewildering was the lack of any further water ingress.  We left her floating on her lines until morning.    Still no significant water in her bilge. 

After towing her to Brundage point she was loaded on her trailer and transported to a holding site for the insurance inspection.   We still could observe nothing that would indicate a fast sinking. 

Subsequent investigation revealed the cause of the sinking.    One of the four bellows that connected the engines to the outdrives had a small hole in it.   This would have allowed water to enter the bilge area at the stern of the boat.    The thru hull for the bilge pump for that compartment was very close to the waterline and as such should have had an anti syphon loop with a valve.  It did not.  All that was found was a very small (6”) loop.   This would do very little to prevent water ingress once a syphon was started.   The Automatic bilge pump failed to start.   It seems that once the leak in the bellows had brought the stern down to the point where water could enter the bilge pump thru hull the boat began to take on water at a very high rate.   Within two hours the vessel was lost.

Lessons:

1.  Make sure that your bilge pumps are connected directly to your batteries with an appropriate fuse and regularly test their automatic function.
2. If the output of your bilge pumps is with in a foot of your waterline then make sure have a riser of at least another foot with an anti syphon valve at the highest point.
3. Regularly inspect all hose clamps and glands that keep water on the outside of the boat.