Strut/Prop Failure

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4-27-06 Update: We still don't know the exact cause of our failure. It is Marine Pro's opinion that the strut broke first, due to electrolysis. We are taking all our parts, pieces and photos to the manufacturer of our boat, who still makes the same boat, to see if they can determine what happened.
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Today we were motoring down the ICW on the Indian River - no wind, but a beautiful sunny day just the same. We were in between two other boats from our sailing club, middle of the channel, headed to an island to anchor for an overnight. I was at the helm, thinking more about hanging the hammock upon arrival than anything going on in the cockpit at the time. I was jolted back to reality by the sound of metal on metal. We coasted off the channel and dropped anchor. With the engine still running in idle, following his inspection of the engine, Chris shouts "shut `er down, there's black oil all over down here." He then dove the bottom and saw that the strut was broken in half.

Fortunately, we were able to get towed and hauled - which was no easy thing on an Easter weekend. There was no impact involved in this failure. The rudder, keel and bottom are very, very clean. We were in the middle of the ICW with 12' water. Also, there doesn't appear to have been anything fouling the prop. We were motoring down at about 2200 rpm - 6.7 knots.

From our preliminary inspection, it appears that the prop blade failed first, and the lopsided, unbalanced, remaining two blades under load caused the strut to break. From the last photo you can see that the prop has two inches clearance between the top of the blade and bottom of the boat. We think that the gash in the boat must have occurred when the prop blade was lifting (as it was failing) and thus elongated enough to reach the underside of the boat. We have folks coming to inspect on Friday, so should know more after that.