Anode Continuity Volvo Saildrive

[Jon magowan]

More help please !

I’ve just replaced the anode on my Volvo Penta saildrive 130S-b. I’m very aware of the need for electrical continuity so took care to clean the metals in contact with each other.

Having finished the job, I checked continuity with my multimeter. Now here is the problem. There is zero electrical resistance between the anode and the oil drain plug on the bottom of the saildrive. Great.

However, there is infinite resistance between the anode and the body of the saildrive. I have dug the multimeter into the saildrive metal and checked it at several places, but no joy anywhere. Very frustrating.

What is going on here ? Your thoughts please……….

 

[QBhoy]

I'd say that it is often very difficult to get a good reading through the painted finish of the drive...and much more difficult again, should there be anti foul on top of that. Really needs to be a clear contact with bare metal to get anything at all. It might put your mind at rest perhaps, with the thinking that if you are getting a good reading of continuity at the stainless drain screw, one might assume that this is surely only possible because it is doing so by conducting through the threads in the casing of the body of the sail drive itself. There may be some sort of continuity through the oil, but to achieve such a reading as you've reported, got to assume that it is doing so through the drive itself ? What do you think to that assumption?

 

[Jon magowan]

Thanks QBhoy. Yes, agree with your logic re the drain plug. It’s just so strange that the drain plug reads zero, yet the saildrive body itself reads infinity.
I think I’ll check the resistance between the plug and the saildrive body ……….

 

[QBhoy]

Thanks QBhoy. Yes, agree with your logic re the drain plug. It’s just so strange that the drain plug reads zero, yet the saildrive body itself reads infinity.
I think I’ll check the resistance between the plug and the saildrive body ……….

Yeah...something I have had issue with loads, when checking the continuity between external hull anodes and stern gear/p brackets etc etc. Very difficult to get a contact through the paint. Can take many attempts and usually results in scratching some pint off to get bare metal. Not that I would recommend that on your sail drive. The oil drain plug being likely stainless and not painted with a finish originally perhaps, would certainly be likely to contact more definitively with the probe. I think I would sleep easy, with the assumption outlined above surely meaning all is well. It's a good post and relevant point for sure. Certainly resonated with me at least.

 

[Alicatt]

If the leg was anodised then that could read infinity.

A friend installed anodised handlebars on his motorbike - then nothing worked, as a temp measure I strapped a copper earth wire to the switches on the handgrips and took that to an earth on the mounts for the handlebars and then everything worked, he was heading off in a rush and this was to get him there and back before I could do a proper job on it for him.
Got a phone call from him 60 miles away, he did not like the small wire I had taped under the handle bar to provide the continuity and ripped it off... then his bike didn't work again at least he paid for my petrol to come and sort it out for him

 

[Tranona]

There is no way you cannot have continuity between the anode and the housing as the 2 are bolted together. You won't get a reading on the outside of the housing because it is epoxy coated before painting at the factory. You get it through the plug because that is screwed into the bare aluminium. You should also get a reading from the anode to the bare aluminium behind the propeller. The bonding is through the attachment screws plus the physical contact with the bare aluminium. Pretty fool proof arrangement.

 

[Jon magowan]

Thanks Tranona. I appreciate your input. You’ve put my mind at rest !