My h40.5 has this recessed area where the prop shaft is inside a tube-like area. Of course the barnacles grow inside and are hard to clean out easily.

The recessed area of the prop shaft

The tool is simply a wooden handle that is attached to a piece of 1.5 PVC plastic pipe. The PVC pipe is cut in half and fastened to the handle.

Here is a tool I designed and built for cleaning

Looking down the PVC tubing from the handle. The tubing is about 15 long. The measurement is not critical as long as you have enough length to reach inside the shaft area and have enough clearance to the strut.

Here is another picture of the tool

The pipe cleaning sandpaper is a waterproof, fabric-backed material that is about 1.5 wide and comes on a roll. One roll will last you a lifetime. Tear off a piece that is about twice as long as the tube. Curl and lay it inside the tube and hold it in place with your finger.

Insert a piece of pipe cleaning sandpaper

Insert the tool with the sandpaper inside and work up and down the shaft. Turning the shaft will ensure that the entire length gets cleaned. As the sandpaper becomes filled with barnacle dust, move the sandpaper so a fresh area is near the end of the tool. Cleaning this entire area takes only a few minutes. Holding the sandpaper on the outside of the tubing also allows you to clean the inside of the recess too. Having the right tool is everything.

Ready to go to work