Anodes

[Sy-Revolution]

Hi ppl,
I was reading the article in PBO (or was it ST) about anodes and it got me thinking..... or perhaps I should say, worrying.......

I bought my boat the year before last and when I had her out last year I noticed the anode on the feathering prop (Variprop) was in need of replacement, so replaced it was, I also added a ring anode to the prop shaft, (there's only about 3in of shaft showing outsdie the hull). I have a flexible joint on the prop shaft and therefore the engine is not protected. We've left her in the water this winter and so the engine (Vetus m4.17) has spent many months filled with briney.

Should I get an anode connected to the engine asap? Is the engine at risk as it is?
Or am I worrying unduly?
I asked about last year and was told not to worry too much as the boat hadn't had an anode for the engine before (she's nearly 30 years old now).

Prior to my ownership the boat was kept at Kiel (baltic) and therefore the previous owner may not have bothered with the extra anodes due to a shorter season and always had the boat out in winter.......

I replaced a faulty exhaust temp sender today and it, (copper), was pinkish...........

Whaddya reckon?

Crispin.

 

[VicS]

Good you replaced the anode on the prop when it needed it. That ought to be adequate so the shaft anode my be unnecessary but it will hopefully make the prop anode last longer although you might find you are simply replacing two anodes when you could have saved the cost of the extra one.

No anodes outside on the hull will protect the engine coupling bridged or not. Flexible couplings are bridged when the stern gear is to be protected by a hull anode which is bonded internally to the engine or gear box. It completes the circuit between anode and sterngear.

The engine can only be protected by an internal anode so it has to be something which is catered for in the design of the engine really. Your engine may not have been fitted with an anode but if it was then it should be changed regularly as advised by the manufacturer or more frequently if that is found to be necessary.

Basically anodes must be reasonably close to the items they are to protect, be "able to see" those items and be bonded to them with a good low resistance electrical connection

You might find the MG Duff website worth a look

Actually surprised that the engine is not indirectly cooled. All modern Vetus ones are.

 

[wotayottie]

As usual, Vic talks sense!

Engines often have internal anodes because the external hull one only gives limited protection. Remember there has to be a circuit created for the anode to protect - the hard wired bit from the anode to the engine is easy but the circuit from the component you are worried about through the electrolyte (ie salt water) to the anode can be a long and high resistance one. On the other hand, the circuit from an internal copper engine component through the water to the iron block its screwed into is a nice attractive short one.

Have heard it said that hull anodes only protect a few inches up the water inlet at best. So check carefully to see if your engine has an anode screwed into its block somewhere.

 

[Sy-Revolution]

[ QUOTE ]
Actually surprised that the engine is not indirectly cooled. All modern Vetus ones are.

[/ QUOTE ]

Yes it is..... indirectly cooled that is, the engines only a few years old. Thanks for the info, you've put my mind at rest, I'll check or an internal anode next week.

Cheers,

Crispin.

 

[VicS]

[ QUOTE ]
Yes it is..... indirectly cooled that is

[/ QUOTE ] I assumed that the 30years applied to the engine as well as the boat.

You also said, "left her in the water this winter and so the engine (Vetus m4.17) has spent many months filled with briney" but it's not filled with briney at all then!

An indirectly cooled engine very probably does not have an anode. You keep antifreeze in the system, just as you do with your car, presumably and the inhibitors in that will prevent any corrosion of the engine's waterworks.
There could be an anode in the seawater side of the heat excahnger, depends on the matrials of construction I suppose.