rafiki_
Well-Known Member
Rafiki eats prop anodes. Hull and trim tabs last ok, but props less than a year. It is a 45mm dia that fits over the prop nut, so no opportunity for enlargement. Any thoughts?
Prop anode
- Thread starter rafiki_
- Start date
Bandit
Well-Known Member
What's the boat, I assume shaft drive?
Consider shaft brushes and shaft anodes, prop nut anodes just do not have the mass if there is a problem.
Consider shaft brushes and shaft anodes, prop nut anodes just do not have the mass if there is a problem.
superheat6k
Well-Known Member
If your shafts are bonded to the engine then extend the bonding to a convenient deck point e.g. the guardrails, then make a dangling anode from some old anodes, but attach these to stainless wire (I used an old piece of rigging wire with a forked end) for the immersed part, copper wire is fine for the final bonding connection above the water. Simply hang the anode pontoon side in the vicinity of the props. This will then take some of the zinc hit.
Momac
Well-Known Member
Would it help to connect a large anode to the gearbox inside the boat ? There is presumably sufficient electrical connection between the gearbox case and the propeller shaft ?
I assume there would be a bolt on the gearbox that could be used to fix an anode using an earth strap.
i may be wrong - just a thought as I am waiting for the kettle to boil for my breakfast cup of tea.
I assume there would be a bolt on the gearbox that could be used to fix an anode using an earth strap.
i may be wrong - just a thought as I am waiting for the kettle to boil for my breakfast cup of tea.
rafiki_
Well-Known Member
Az 39 on shafts. I'm not sure how an additional anode on the gearbox is going to work. Sorry if I'm being thick, but also ruminating over breakfast coffee. Trevor, I like the idea of the dangling anode, but can I take this straight to the shaft? Not sure how I would attach to a guardrail reliably?
Momac
Well-Known Member
Does an anode have to be in the water ? Engine anodes aren't submerged and I assume they work ? (I dont have any on my engine).
Phildorset
Well-Known Member
the dangly wire option is pretty good, Iow tech & good, I might go this route as I opted to ditch the shaft anodes this season (didn't like the idea of them flailing their way past/through the props as and when they dissolved past the point of being fixed), am waiting to see if prop anodes alone are man enough for a season at a time?
Rafiki, yes, you can take the wire direct from the shaft/gearbox or engine... but then you have a long wire and possibly an open locker/engine hatch, I took it that the idea was to find a good point in the engine room that gave you a path for you to then attach your wire to on the topside, and then clip onto and dangle from there.
Rafiki, yes, you can take the wire direct from the shaft/gearbox or engine... but then you have a long wire and possibly an open locker/engine hatch, I took it that the idea was to find a good point in the engine room that gave you a path for you to then attach your wire to on the topside, and then clip onto and dangle from there.
RIN
Well-Known Member
you could drill through the rudder(s) and clamp anodes somewhere near the props. Also consider a hanging anode near to the props. We are going to be doing both these things next year
Bandit
Well-Known Member
When the boat is out of the water check the electrical connectivity of all underwater metal to the anodes, resistance should be less than one ohm iirc.
check anode wire terminals for green connections or black crumbly cable, clean and replace as required to get good connection. If you need to use new cable use tinned cable which is much better in a bilge against corrosion.
To give any protection to the prop the anode needs a good electrical connection to the shaft and prop.
Some shaft couplings such as R&D need to be bridged with a wire across them. Even so electrical connection is not always good through a gearbox and engine.
I would go for shaft brushes for both shafts either connected to an existing anode close to props or fit an additional one. Belt & Braces, I have brushes and shaft anodes.
check anode wire terminals for green connections or black crumbly cable, clean and replace as required to get good connection. If you need to use new cable use tinned cable which is much better in a bilge against corrosion.
To give any protection to the prop the anode needs a good electrical connection to the shaft and prop.
Some shaft couplings such as R&D need to be bridged with a wire across them. Even so electrical connection is not always good through a gearbox and engine.
I would go for shaft brushes for both shafts either connected to an existing anode close to props or fit an additional one. Belt & Braces, I have brushes and shaft anodes.
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VicS
Well-Known Member
I am sure MartynG means an external hull anode bonded internally to the gear box.
Yes an anode must be in the water.
It must be reasonably close to what it is to protect and it must be mounted where it "can see" the item, ie not shielded from it.
There must be a good electrical connection between the two. In the case of a hull anode this may mean using brushes running on the shaft inboard of the stern gland eg using MG Duff's "Electro eliminator" (q.v.) or by bonding it internally to the engine or gear box. In the latter case any flexible shaft coupling must be bridged to complete the electrical connection.
Engine anodes, when fitted, are mounted in the seawater flow through the engine or heat exchanger .
How will you make the electrical connection between the anodes mounted on the rudders and the props ?
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RIN
Well-Known Member
Mine are bonded via the rudder stock. I would imagine this is normal but its my first boat on shafts so I am not sure.
NoviceRod
Well-Known Member
Do you have a galvanic isolator? My MF705 did not, and ate the prop anode.
So I had a GI fitted to my Nimbus 335, and the prop anode does last the whole year (just)
So I had a GI fitted to my Nimbus 335, and the prop anode does last the whole year (just)
rafiki_
Well-Known Member
Yep, isolator fitted. Main anodes do well, it is the props that get eaten.
Bandit
Well-Known Member
Prop anodes are a very small mass/surface area for good protection.
Do a continuity test and see what is connected to what and the resistance.
Do a continuity test and see what is connected to what and the resistance.
gordmac
Well-Known Member
Add shaft anodes?
superheat6k
Well-Known Member
The gearbox idea would be brilliant if the gearbox were immersed - Clipping on the shaft is likely quite a pain, so if your shaft is bonded to the engine and boats negative then any where you can attach to negative would work. A large croc clip makes attachment to a stanchion or rail simple, but you must get in the habit of hauling it in as part of your pre-sailing routine.
The top of the river can be quite a patch for stay currents - I assume you have a GI fitted.
QBhoy
Well-Known Member
Probably already mentioned, but when out the water (preferably), get a multi meter, set to ohms and check the continuity between items. They should all be connected inside the boat by a line of earthing wire. Usually from earth to shaft gland, to p bracket, to rudders and to the main anode on the hull. The reading should go to "0" in a perfect world, but usually close as damn it is good.
It's something I check on the old mans boat every year after finding one of the connections corroded. If this is the case, the whole thing is useless.
Twin engine set ups are obviously x2.
Hope this helps.
It's something I check on the old mans boat every year after finding one of the connections corroded. If this is the case, the whole thing is useless.
Twin engine set ups are obviously x2.
Hope this helps.
QBhoy
Well-Known Member
Should have mentioned, the above set up, usually means you don't need a prop anode.
Portofino
Well-Known Member
Bin the fixation with 12months --where did that exactley come from ? Show me the evidence ps ?
Replace anodes when they are deemed worn 1/2 or what ever worn , current opinion advises .
This may mean in certain situations like props , the shaft , the bolts , the p bracket ,the cutlass bearings , the coupling inside , with all those dissimilar metals there's a lot of potential electrolytic activity leading to rapid prop anode wear ,not making a 12-/12 time line .
Change them when ready ,regularly inspect etc .
I can Snorkel them and have a mini diving kit .The Med issued really relates to a wet suit or thickness of wetsuit .
Cold water UK does not automatically mean they have /need to be done @ the annual lift ! Conveniently that may be .
Replace anodes when they are deemed worn 1/2 or what ever worn , current opinion advises .
This may mean in certain situations like props , the shaft , the bolts , the p bracket ,the cutlass bearings , the coupling inside , with all those dissimilar metals there's a lot of potential electrolytic activity leading to rapid prop anode wear ,not making a 12-/12 time line .
Change them when ready ,regularly inspect etc .
I can Snorkel them and have a mini diving kit .The Med issued really relates to a wet suit or thickness of wetsuit .
Cold water UK does not automatically mean they have /need to be done @ the annual lift ! Conveniently that may be .
rafiki_
Well-Known Member
Nice thought. So could you pop into the Hamble on a regular basis for a look please? Not sure I fancy that much ��