[C320-list] Blade falls off of Autoprop propeller!

[WindSwept]

A funny thing happened on the way to the ship yard this spring for my semi-annual bottom job.  Well maybe not so funny.

Carla and I spent the night at anchor in a cove about 1/2 mile from the yard the prior to dropping off WindSwept.

After hauling anchor when we tried to motor over to the yard the boat shook terribly at any RPMs above idle.

We quickly anchored again and I dove below the boat to find out what was wrapped around the prop, but was amazed to find that one of the three blades of my Autoprop was just......missing!

We managed to sail to the yard which is located up a narrow channel and moor in the haul up slip.  Luckily the wind was from a favorable direction.

To make a long story shorter, I had the fixed three blade that came with WindSwept reinstalled and sent the Autoprop to AB Marine for analysis and repair.  The prop had to be sent back to the factory in the UK so the engineers could look at it and a new blade could be fabricated.

The reason for the failure was that the bearings were excessively worn causing too much torque to be applied on the mechanical fastenings that hold the blades on.  

At this point I think it is relevant to mention that I had purchased the Autoprop used about 7-8 years ago from a 320 owner who had traded up.  I do not believe I received all the paperwork that one would normally receive with a new Autoprop.  This paperwork discusses the need to inspect and adjust the bearings at each haulout.  AB Marine sells a kit for this purpose.

I was upset with AB Marine as through the years I have had many discussions on this subject and even though I asked about maintenance, this was never mentioned.  In their defense, they probably thought I had the original instruction sheets for installation and maintenance.  As an engineer I was amazed that I didn't need to do any maintenance on a bearing in this type of service.  The autoprop had been on WindSwept for four years without maintenance before the failure occurred.

The point of all this is that I think this was a preventable situation had I know to inspect the bearings for excessive looseness and adjust every year or two as needed.  

I plan on having the Autoprop put back on in a couple of weeks as I can definitely say it really improves boat speed and handling in all situations.  I will inspect it annually and disassemble and adjust bearing clearances every other year at a minimum.

I wanted to share my experience with others in the hopes that you don't experience the same problem.  In another situation it could have been much more disastrous.

Larry
WindSwept C320 #246