Autoprop H6 blade removal – take 2!
In this post we continue the blade removal from the Autoprop H6 sailboat propeller and remove a single blade ready for rebuilding. Previously in Part 2 we had struggled to get one of the blade caps off the propeller despite using a wide range of tools including the odd large hammer and sharp words! Working late into the night we discovered that a bit more leverage was all that was required. Using a 4 foot length of pipe we inserted the peg spanner into the pipe, held the blade securely on the bench and hey presto the seals on the caps broke. once the seals were broken the cap could be wound off of the propeller and the inner workings of the blade could be seen for the first time.
Blade Cap removal
Once the blade cap is removed, inspect the cavity for grease – there should be plenty! At this time it will be a good idea to locate and remove the O-ring that seals the cap. For this video, it had hardened and was in need of replacement. The threads on the blade cap are also very fine so care should be taken when re-fitting the cap or indeed cleaning all of the gunk off of the cap.
With the cap removed it is now possible to start to remove the fasteners holding the blade in position. The remaining steps are relatively straight forward and if the blade bearings are well greased, should not present any issues at all. To remove the tab screw, find the one tab that has been bent into the blade nut and lift it up with a small screwdriver – this will free up the tab screw to be removed.
On each tabscrew you will notice two holes, this is the seating for the peg spanner used to wind off the tab screw. You will also notice a ‘LH’ etched on the top of the screw, this denotes that it is a left hand thread and must be wound clockwise to remove. However the tabscrew has also been bonded in place with loctitie and may require some persuasion (heat or force) to unwind from the propeller.
Propeller Nut Removal
With the tabscrew out of the way the propeller nut is now visible. This is a simple nut to remove with the nut spanner and it does not typically have a lot of force keeping it in place. Take care to hold the blade steady as once the nut is removed, parts can spill everywhere! In the video we did not restrain the propeller for for the camera, however it is better to have everything clamped down in place if possible. With the nut removed the blade is free and can be worked loose by rocking side to side.
There are two sets of bearings inside the blade cavity. The first is a taper roller bearing, this is a crucial bearing and note that the large diameter of the bearing faces outwards. If you replace this bearing backwards (small diameter facing outwards) only the tabscrew holds the blade on and after several rotations it will launch itself to the bottom of the ocean. This bearing sits in a pocket on the blade and should come away with the blade.
Thrust bearing removal
The second bearing is the thrust bearing and transfers the hydrodynamic load of the blade to the shaft to propel the vessel. For the H6 propeller this consists of two races, one in the hub, one in the blade and a caged bearing race. If the blades have been greased then removal is a piece of cake. The crucial thing about the H6 propeller is that all of the wearing parts are replaceable, giving the propeller a tremendously long service life, if taken care of.
Signs of Trouble
In the next post we will start to remove the bearings and seals in preparation for cleaning the propeller. It is important at this point to understand the condition of the bearings. If the bearings still have grease on them and turn freely, there should be no cause for concern and a careful de-grease should yield no surprises. If however the bearings are rusty then there could be other things going on and a quick phone call or e-mail may be needed to verify the condition of the blades. Sometimes the propellers are simply too degraded, most times however there is a fix to be had from the factory!