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      Hi all,
      The boat (Bav 36 with Volvo 2 bladed prop) was lifted last week and I went down to her yesterday.
      Very pleased with how clean she was after 22 months apart from a lift and hold to change the anodes last January, but for the first time ever there was very little wear on the saildrive and prop anode (3 segment that normally barely last the season).
      In fact there was so little wear that I could have left them in place which makes me think I have a problem somewhere that could end up with the leg starting to suffer as the anodes aren’t, although there is no evidence of this yet (well as far as I could see)
      Not being that electrically minded any hints and tips on what and where I should be looking for will be appreciated.
      The boat is in the same berth as always in Chichester Marina so no change this year to previous.



        Hi Rick

        Did you do the trick with the paint round the screw holes (to stop the rapid erosion here that results in the anodes flying off)? If you did, then it could be the paint was insulating the anode too well. There must be good electrical contact between the anode itself and the brass of the prop boss (but ideally not round the screw holes).

        If you didn’t have any additional protection (paint) on the anodes then you could do a quick resistance check that the prop is isolated from the saildrive leg and the shaft – it should be; the prop is rubber mounted

        If its neither of those, has there been any change in usage this year e.g. more/less motoring; more/less shore power?

        Also, any change in electrical equipment – galvanic isolator, new battery charger, wiring changed etc.?

        I think you are right to be suspicious = something must have changed!

        Good hunting.



          I had a feeling that you would provide the first response to this one, and you may have hit the nail on the head with your first paragraph.
          When I fitted the anodes on the prop back in January during a 1 hour lift out I didn’t have any paint with me so used Threadlock and fully coated the thread and underside of the screw.
          When I took the anodes off yesterday there was a surplus of threadlock between the anode and the recess in the prop hub which could easily of been holding the anode off the hub therefore a poor contact. As you know when using Threadlock the surplus gets forced up and out out as you do the screw up.
          I cleaned and polished the prop and hub yesterday but will make sure that I only coat the screw hole of the anode before I refit them next time.
          Thinking about is as well I have not plugged in anywhere near as much this year either.
          Thanks for the pointers on the obvious but I will also check the resistence between the prop and the saildrive just to be on the safe side.



            Can you please explain “the paint around the screw hole trick” in more detail. I have noted that the three anodes near the prop do erode very quickly on our B36.




              Hi John

              The problem arises because the anodes erode quickest where there is best electrical contact between the hub and the anode. This is generally around the fixing hole under the bolt head with the result that the anode flies off as the hole enlarges, although there may be half the anode left.

              The ‘trick’ is to reduce the electrical conductivity in the immediate vicinity of the fixing hole and the easiest way to do this is to put a thin layer of paint under the bolt head and right around the anode at the fixing hole.

              I was losing all 3 anodes in less than a season before I started doing this. Now I can go 12 months (just) between anode changes.

              If your 3 anodes are still attached at lift out then you probably don’t need to do this. They do erode quite quickly.


              PS Don’t overdo the paint, though, as there still needs to be good contact between the hub and anodes for them to work!


                I have tried painting around the screw holes on the anodes but I do not seem to have been as successful as Roger. I have been wondering about putting a small fibre washer on the bolt instead. Any comments on this idea would be welcome,

                Regards, John


                  Sounds like a good idea – give it a try and let us know if it works any better than the paint (in 12months or so)! It might be even better if could isolate the shaft from the anode of the bolt as well.

                  I wonder if the erosion of the prop anodes is more a function of engine hours (or prop revolutions even) rather than time? In theory, there is no circuit between the prop and anything else on the boat (i.e. it’s insulated) so shouldn’t be subject to galvanic action at all.

                  No, I don’t fully understand it either!



                    An old thread but another contribution.

                    I had our 37 in Chatham marina for the first year on a pontoon with occasional shore 240v supply – isolator fitted to stop electrolitic action. At the first lift at the end of the first year the prop anode was half gone.

                    Then moved to a buoy on the river. After 3 years very little prop anode erosion. Looks like shore power causes the problem even with an isolator fitted to the boat.


                      @achilles/medway wrote:

                      Looks like shore power causes the problem even with an isolator fitted to the boat.

                      I agree, my B32 was in Ocean Village from Jan-May this year.
                      The shorepower was plugged in and on 24/7 to keep the boat warm/dry etc.

                      On lifting the small secondary hull anode was almost gone whilst the prop anode only shown signs of slight “pitting”.
                      Had I not lifted her though, I am sure that it would not have been long at all before there was nothing left.

                      I thought that the isolators fitted to the boat were supposed to reduce this issue?
                      Or is it just a poor supply issue at the marina?

                      I for one will think twice before leaving the mains on for so long next time.


                        I dont a lot about the subject but I understand it is not simple. The variable so I understand it is the boats around you and what they are doing. certainly being plugged in to the mains is detrimental and I can only assume that without an isolator it would be worse.

                        Some people hang an anode over the side of the boat which becomes sacrificial but I dont know where you connect it assuming it is not just hung from a safety line.

                        I hope to move to a marina soon so I’m concerned. I have an Ambassador cutter fitted which has to have a modified prop anode from them, so it gets a bit expensive with postal service etc and I may have to change it every year.

                        Expert comments please – what do you do in marinas with a shore supply to reduce anode erosion?


                          As far as I know, the engine, saildrive, and hence the prop anodes, are electrically isolated from the battery negative except when the key switch (“ignition”) is operated – there is a relay that connects the engine to battery negative when the engine is ‘on’ so the glowplugs and engine stop solenoid etc. can work. Given that there should be no connection from the mains earth (or mains neutral!) to the engine etc. I can’t immediately see how mains connection should increase anode erosion.

                          That said, except when we are aboard, I do not leave mains connected, as I have a sneaking suspicion something strange happens like you describe. In the winter I connect the dehumidifier and small heater direct to the mains cable and not via the boat circuits.

                          I would love to understand the science here!

                            playtime wrote:
                            In the winter I connect the dehumidifier and small heater direct to the mains cable and not via the boat circuits.


                            Sneaky simple solution…. I like it!


                              I realise that i am quite late in this discussion, but my vintage 1996 Bavaria Holiday 35 only has 1 anode, and i have an Abassador rope cutter fitted which needs a modified anode, which i believe helps to retain the anode and stop it falling off, although i have never lost one. However i have never painted the anode around the head of the fixing bolts as they have never worn away the anode, all i get after around 12 months is an eaten away anode at what would be the vertical sides of the anode.

                              Ed Holmes Storm Dragon


                                Hi Ed

                                The paint trick is used on the 3 small anodes that fit around the periphery of the boss with a folding prop.

                                The big hub anode, concentric with the shaft, only erodes slowly and I agree, does not need any paint or other tricks to prolong its life!

                                Maybe this wasn’t clear in previous posts.



                                  Hi Rog

                                  All i can say is glad i do not have a folding prop, do you think your folding prop gives you less drag and more speed when sailing and justifies all the problems with the anodes.


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