130S-C sanding confusion

[robbadgie]

Hello, I recently bought a yacht with this sail drive. It had barnacles on it and I want to repair the surface. There are no chips or cracks. I am utterly confused about which parts of it I can sand and with what paper.

The operator's manual that came with the boat (dated 2016) says "Lightly sand metal surfaces using emery paper grade 120. Use a finer grade paper on painted surfaces."

The workshop manual I find on line for the sail drive says "Remove all loose paint and corrosion residue by grit blasting or sandpaper..... If sandpaper is used, it must be coated with aluminum oxide. Sand painted surfaces and the damaged/corroded raw aluminum surfaces to be touched up......IMPORTANT! Do not use emery cloth. Small pieces of iron oxide which are used in the emery cloth will become embedded in the aluminum and will cause severe corrosion damage."

Is anyone able to explain to me what I should do (preparation and finishing) with the sail drive leg and also the metal parts (between the two anodes and the prop itself).

Thank you

[JEN-et-ROSS]

I wouldn't bother sanding it.
The surface coating is important to protect the aluminium casing beneath it so why risk damage, others may disagree.
We just carefully remove any loose antifouling and marine growth.
Inspect it for nicks or other breaches in its defences.
Clean out the engine cooling water inlets and internal water riser. (A straightened wire coat-hanger is excellent for dislodging unwanted guests from the riser)
Then a coat or two of Trilux 33 followed by new folding prop anodes, obviously don't paint the anodes, the leg anode/s on sail drive casings often to last for years.
Since the leg tends to be out of sight and nobody can see it, to make it shine seems pointless. Although a spotless prop is another matter indeed, it's worth giving it a good polish.......Bill.

[symphony2]

Agree fully. The stuff in the manual is only applicable if the coating has failed. You don't say if there is any coating on it already in addition to the original paint. Normally Trilux or the Hempel equivalent is used, often black. It is not a particularly good antifoul, but is the only thing you can use. Barnacles do grow on it but they can be scraped off. IF you do have Trilux you can safely sand it to give a key for the new coats. Do not coat the anode or the bare aluminium behind it. I Leave the anode on and cover it with masking tape so it is safe to spray the whole assembly then remove the tape. If you have an aluminium fixed prop you should spray that as well. If it has not been coated before, clean it, lightly abrade and then use Trilux primer and top coat. If you have a bronze folding prop then it is worth putting the effort in and coating it with Velox, at least the blades. On my FlexoFold 2 blade I use Trilux on the hub and spray it at the same time as the housing, and white Velox on the blades which remain free of fouling apart from a slight slime, even though the boat is more or less permanently in the water.

[robbadgie]

Thank you both for your advice. I've attached a picture of it - it is missing a set of anodes in this picture. I'm not entirely sure its ever been treated. Is that the original colour for the leg? Can you explain what you mean by the bare aluminium behind the anode - I can't see what you're referring to?

So your recommendation would be Trilux on the leg (plus a primer? and if so what do I sand it with beforehand) and the hub between the anodes. And primer/Velox on the blades?

Thanks again!

[symphony2]

Yes, that is the original finish on the leg. The dried on slime needs washing/scrubbing off and then abrading with120 wet and dry. The coating is very robust and will stand the abrasion. Then prime and coat with either Trilux PropoDrev or Hempel Ecopower which is a bit cheaper. Mask off the anode up to the painted part of the leg. The bare aluminium I mentioned is behind the anode, where there is also a stainless carrier that the anode is mounted on, but it won't get coated if the anode is in place and masked.

antifoulingpaint.net will give you the instructions for Velox which is available from chandlers such as Force4. As you will see there is quite a bit of work involved in the preparation and you will have to remove and dismantle the prop so that you can prepare the hub and blade castings. If you do go down this route, do not paint the groove the prop anodes sit in as the anodes rely on direct contact with the bronze to work.

In my view well worth the effort, particularly on the blades as fouling can seriously affect performance. After a year in the water my blades just needed a wipe over and the Velox is still firmly attached to the metal.

[Keweetoo]

I have the same Volvo Penta folding prop and the three part split anodes rarely last more than 6 months. I generally have a quick lift/wash and replace them in autumn and have the boat out in spring for antifouling and replace again. I have found painting a band about 1 cm wide around each anode where the retaining screw goes helps stop them dropping off prematurely.  Regarding the prop I have tried various antifouling types but found that no coating is the best - I polish to a bright finish with power drill wire brush and polisher and this high polished surface keeps the critters from getting attached but much will depend on your sailing/mooring area and the degree of fouling in your home water.

[symphony2]

The Volvo propeller that you have is notorious for short anode life. Combination of a poor (compared with other makes) alloy for the hub and blades plus a lot of stainless in the gearing, particularly with the 3 blade, My FlexoFold 2 blade has been in the water continuously except for annual 10 day haulouts since 2011 without any anodes at all and is still in perfect condition. Their 3 blade has small button anodes which seem to erode very slowly.

You may well find value in coating your hub and blades with Velox as I explained above. Not only is it an excellent antifoul, but it reduces the surface area of the alloy exposed to seawater and may well reduce the galvanic action between the alloy and the stainless gears and fastenings. I know others who have had success with this on Bruntons Autoprops which are also heavy on anode wear.

[robbadgie]

Many thanks for all your suggestions