Old anode / cathode system?

[GrahamHR]

The Mercathode manual from Mercruiser states that stainless props upset the ratio of anode to cathode, so unless Mercruiser are repeating an urban myth.....

They are referring to their product. Bravo 3 props by their design have the stainless props directly, mechanically and electrically connected to the rest of the drive, so yes, for their design it probably does lead to extreme sensitivity to anode type and condition. They have revised the anode number and location numerous times for that drive, even putting one on the end of the propshaft..

Volvo Penta props have an insulating bush between the stainless ( or nibral) props and the aluminium hubs. The stainless is not electrically connected to the drive or anodes, so their presence does not affect anode wear rate.

 

[TheOrs]

I had this problem. I believe it was due to the high tide range where I am. Is there a lot of water movement (tide/current) where you are?

My fix was to repair my MerCathode & add a couple of additional anodes on the transom (grounded, of course).

My anodes now last a year.

Why you say they should not be connected to any Volvo set up ....

I think it was tongue in cheek.

What, this urban ( or marine) myth again? I have never seen any scientific evidence that this is the case.

If the anodes are not electrically in contact with stainless props they will not protect them or erode due to them. Volvo stainless ( DPS) and nibral (DPH) props have a plastic bush that isolates them from the drive/ anodes.

It's true of Mercruiser as the prop is electrically connected. I have no idea about VP but I'm sure you're right.

Can you pass on the link to this manual Martin? I'd like to get my hands on a copy. Ta

Try here: http://www.boatingwithtr.com/members/pdfs/7a_28.pdf

Darren

 

[GrahamHR]

The aluminium anodes I use on my Volvo DPH with the Volvo ACP system last at least 1 year., they'd probably last 2+ years. My previous DPS drive I had with the ACP system, well, the anodes lasted 3 years and I used to change them out of "guilt " as they were by them ca 2/3 gone.

I wonder why Mercruiser persisted with the integral hub and associated electrical contact with the drive for Bravo 3 props, when they use rubber/ plastic bushes on other drives.