This time of year, when the boats out of the water for the winter, is a great time to check the condition of your boat’s anodes, cutlass bearings, shaft and prop for the coming season.
Anodes are often overlooked and sometimes considered to be of a low priority.
Merely talking about anodes can be confusing with numerous books written on the subject and many, at times conflicting, ideas and guides provided.
The sad fact is that if you avoid looking after your anodes correctly, the consequences can cost a fortune to put right.
As a boat owner myself I don’t like spending money if I can help it, especially on something that is designed to dissolve away to nothing.
The temptation therefore is to spend less and buy cheaper anodes that coincidentally happen to dissolve slower.
Do NOT do it.
The simple truth is that its far better to spend money on quality anodes that work correctly than have to pay for a new prop, shaft or sail-drive leg.
With wooden boats, you also need to be aware and guard against the potential of electrochemical decay of your timbers.
We’ve seen cheap anodes that customers have fitted, usually sourced via ebay or similar, that frankly have not worked. Often they look just as good after a season as they did when first fitted, which is obviously a bad thing.
As a general rule the larger the surface area the higher the current capacity or galvanic voltage it can handle.
The heavier the anode the longer it will last.
The higher the purity of Zinc the more efficient it will be.
On a grp boat its preferable to link or ground your anode internally to the propshaft.
Some manufacturers ground out the anode on the engine block or engine mounts but quite often the prop shaft is electrically isolated from the gearbox and engine using plastic bushes and inserts, rendering the connection pointless.
Some Volvo gearboxes, for example, use an internal copper pipe matrix for cooling and to avoid corrosion they are electrically isolated from the engine and add a less than helpful notice on the gearbox, “Do Not Ground”.
In these cases, if there is no room for an external shaft anode, you must ground directly to the shaft using an Electro-Eliminator from MgDuff or similar system.
On an Ovni we discovered that the grounding wires were linked through the boat’s main isolators, which meant that leaving the boat and turning off the isolators, would also inadvertently turn off the grounding wire to the anodes. Also not very helpful, especially on a aluminum hull.
Most of the folding and feathering props have their own specific anode but this is really only there to protect the prop and not the shaft and P bracket.
These prop anodes are often quite small and normally these won’t last more than a season and in some cases only 6 months.
Quite often when we lift a boat out, the prop anode will have gone completely.
This is normally due to the anode dissolving around the fasteners and simply dropping off.
A tip here is to dab a blob of antifoul round the fastening bolts so that the anode round the bolt does not dissolve. Alternatively, you can use plastic fasteners instead of the often supplied Stainless ones.
Work on the basis that the prop anode is just looking after the prop.
Anything else, such as the Propshaft, Propshaft tube, P bracket and even below water line pintle and gudgeon, will need their own local anode protection.
Usually a decent sized shaft anode will do the trick and avoid the hassle of internal linking.
This is also a favourable method with wooden boats as there is a possibility that any exposed wet wood between a linked anode and the protected metal object, can effectively close the circuit which will result in electrochemical decay: rot in other words.
If you keep your boat in a marina, hooked up to shore power, then I’d highly recommend you fit a galvanic isolator to guard against stray electrical currents.
Your boat may be just fine with no stray outputs, but the boat two berths down could easily be fizzing your anodes away.
For those of you with aluminium boats or a sail-drive unit this really should be a priority.
When we lift a boat out I usually grab hold of the prop and give it a good tug, side to side, up and down.
Any movement lateral movement here means that the cutlass bearing needs changing.
If it’s not changed you will experience vibration under load and when reversing you will be able to hear and feel some knocking.
The wear will increase and you run the risk of damaging the engine coupling and propshaft seal and if fitted with a folding or feathering prop, you will wear out the moving parts very quickly.
We find that many boats fitted with folding props, especially the Auto Prop, tend to wear out the cutlass bearing faster than a conventional fixed prop.
Our theory is that each time you move from forward to reverse the prop changes angle abruptly and this rapid change contributes to increased cutlass bearing wear.
Changing the cutlass bearing can range from a 15 minute job to a full days nightmare depending on configuration and with so many different types and styles its really beyond this article to offer much advice.
Stainless steel propshafts are usually pretty resilient.
However we’ve seen our fair share of broken ones and others that have been almost cut through by, believe it or not, old fishing line.
If there’s a problem it’s usually where the shaft exits the hull but most fail around the key-way where the prop locates.
Its worth popping the prop off and periodically checking that the key is in good condition and that it’s a nice tight fit with no lateral movement.
Fixed props are easy to check and usually it’s just a matter of inspecting the blades for pitting and that the edges are clean and fair, the locking nut is torqued up correctly with a locking pin in good condition and ensuring the boss is fully home on the taper and key-way.
Ensure the key is fully set down into the shaft key-way and that there’s no grit or muck under it.
The danger is that the prop will tighten up on top of the key and not sit completely down onto the taper.
Check for an air gap above the key if you can.
We had a situation a couple of years ago where the propshaft key had sheared.
All seemed fine ashore. When the boat was launched all appeared good whilst in forward gear, as the prop was pushed hard against the taper.
However putting the boat hard into reverse broke the taper and the shaft just span round with the prop essentially stationary. So it can and does happen.
Folding and feathering props are somewhat more complicated as many have a lot of moving parts that will wear out and some have internal rubber bushes that can fail.
I know this to my cost as the vulcanised rubber bush inside my Gori two bladed folding prop decided to come adrift of the main hub, just as the new season had started.
This had to be sent back to the manufacturer in Denmark who then sent it on to somewhere in Belgium to be repaired. They, in turn, sent it back to Denmark again before returning it to me with a bill for £450 for the privilege, losing me a quarter of the season – not that I’m bitter or anything.
Most manufacturers sell full service kits for the types that use bearings such as the Auto prop from Bruntons.
It’s a straight forward process to replace the bearings and the hardened bearing races, then setting up the blade torque required.
The Max prop is a little more complicated as you’ll need to note down the corresponding letter marked on the hub to maintain the correct blade angle.
One of the more satisfying jobs is cleaning up a dirty prop.
My usual process is to start by cleaning off most of the stubborn muck using a wire cup brush on a drill.
This is followed by 600 and then 1000 grit wet and dry sandpaper, finishing off with cutting compound and a buff and often the final result is as good as new.
Over the past few years we’ve fitted a lot of Feather stream props from Darglow, who I may say are an excellent company to deal with and so far we’ve had few problems other than the usual stupidly small prop anodes they come with.
If you’re in the market for a prop you can phone them, tell them your boat make, displacement, engine size and importantly the gearbox number and they will tell you what size and pitch prop you will need and so far they have been spot on every time.
A year of so ago we carried out a prop switch from a fixed to a feathering prop. During the process, based on the gearbox number, Darglow pointed out that the original right handed fixed prop should have been a left handed one.
Funny to think the owner had only recently finished a trip to Cape Horn and back, it now appears that he did a fair chunk of the journey in reverse!