Boats & stuff [03] - Polishing the propeller

The bronze propeller gets a litle corroded after a season, even in the baltic sea. Polishing it makes it look much nicer, and probably improves the performance a bit as well. Using a high speed polishing disk, it is a quick job. I do not bother to polish the hub. This propeller is probably the same age as the engine = 40 years. Note it is a left oriented propeller, in this case indicating an old Volvo Penta MD17C. The engine is very reliable, and I do not dare to replace it with something modern until I have to :-)
#propeller #polishing #boat #sailboat #sailing #DIY

[@learemington1700]

I use a non ferrous wire wheel on a corded drill. Sometimes a nylon abrasive wheel. (No scratches) then polish with a drill buffer wheel and compound. NEVER a grinder.

[@erikwestrheim804]

Nice and easy, was looking for this thanks.

[@petera9757]

Glad to be of help.
Yes, it does not take many minutes to do. For many years I did not use an anode, but used the propeller to protect the engine, so it corroded quite a lot each year, so polishing was essential. Now I use an anode, but I still polish it. The fixed propeller I have is not very expensive (although a bit hard to find as it is counter clockwise) so not so worried I might be wearing it down. But with the polishing disk, I am not really takin any metal off.

[@runehansen4707]

this is strictly speaking not polishing. it's grinding. I use a red sanding pad to clean. then I use a dedicated metal polish bar and a drill. autosol also works great.
but for a mirror-gloss surface, metal polish is the best🛥

[@jimclark2502]

That might work on a sail boat where the props spin at low RPM's but I would be concerned you will make them out of balance if used on a power boat without balancing them prior to use.

[@petera9757]

The corrosion and biology will of course also cause inbalance, but I agree that on a powerboat you might not use a 43-year old propeller.

[@Mikeandlucy1]

@@petera9757 Of course if you were planning to set a new World Water Speed record in you 40+ year old boat, I'm sure you would have taken the time to check how many microns thick each blade was, how many grams you had removed and making sure you did not alter the profile of each blade in any way. I'm also convinced you would have made sure that any sanding marks all ran in exactly the same direction so as to guarantee the prop gave a perfectly symmetrical amount of propulsion with each revolution. However, I suspect you thought ' hmmmm, Jim's talking bollocks, its a 40 year old boat, not really built to race against a jet boat, also the prop is covered in sea life and is probably as much out of balance already as a sailor after a night ashore and two bottles of jack Daniels, I doubt it would make even the tiniest of a difference if I use a polishing disc on it, so heck that's what I will do'. However, I strongly recommend you take Jim's advice and any planned high speed stuff, you make sure that prop is as finely tuned as is humanly possible.

[@Mikeandlucy1]

IDIOT, you think he doesn't know that, its not a power boat its a sail boat so why even raise the issue. I have however given Petera9757 some useful advice and suggested he take on board your knowledgeable comments.

[@petera9757]

@@Mikeandlucy1 Yes, I do this mainly for fuel economy not speed. And even if I am only polishing, I am of course removing the corroded material so the blades continously get thinner. I would argue that the corroded but non polished blades would have the same or at least very similar history. It is absolutely getting close to replacing the propeller,
which I am sure will be a nightmare as I do not know if it has ever been taken off. Big puller and lots of heat will be needed I am sure, but I dare not try without having a new propeller ready.

[@johnnieholt1188]

Can you post the manufacturer and model of the polishing disk? Thanks.

[@petera9757]

I do not know the brand, there was only one type of polishing disks at the store. This was a 115 mm disk, and there were mainly two types: the grinding ones, which has like laminated sand paper (do not use these, they will grind away the metal), and then they had the polishing type I used, which instead has pads, a bit soft, like the scotch brite pads. I doubt we have the same brands here in Sweden anyway, but if you ask for something to polish metal you should find the right thing. It had three levels of roughness as well I think, I believe I used the medium one. I have also used it on stainless, after having cut and grind it, to polish it up to perfect shine.