Aluminium or Zinz Anodes for Outdrives

[Jurgen]

While searching ebay and other sites recently for an Anode kit for Bravo 2 outdrives I found some very reasonably priced kits.

These said they would work in Fresh, Brackish & Salt Water then went onto some speel about GCSE Science.

I was under the impression (possibly wrongly) that Zinc was the preffered Anode material for salt water?

Any thoughts!

 

[gravygraham]

I was under the impression ( . . . . ) that Zinc was the preffered Anode material for salt water?

Correct.

 

[Jurgen]

Correct.

?????

Correct that Aluminium is best or that Zinc is best?

 

[Beamishken]

zinc usually is the prefered material however mercruiser had problems especially with the b3 with stainless props eating the anodes up too quickly & then starting on the drives so they started using alluminium to make them last longer

I assume its a poorer grade ally than the drives are made from

so you can use either but keep an eye on them as they can be gone in 12 weeks

 

[Bandit]

Jurgen what make and model of outdrive and where do you keep your boat, seawater, freshwater or mixture ( estuary).

 

[Greg2]

Actually, when I researched this aliminium appeared to be a good as zinc in salt water and if manufacturers claims are to be believed they last longer. Anyway, we switched to aliminium on our VP drives and they were fine and did appear to last longer. They also have the benefit of working in both salt and fresh water.

 

[Jurgen]

Jurgen what make and model of outdrive and where do you keep your boat, seawater, freshwater or mixture ( estuary).

Bravo 2, keep the boat in seawater.

Notices that the Port Ram anodes had almost dissapeared whereas the stbd rams were untouched.

Also the small round anodes that sit @ the from of the drives where as new but the anodes @ the rear of the drives were nearly gone as well?????

 

[Bandit]

I would have expected it to be zinc. I dont know a lot about mercruiser, what is the props stainless or aluminium?

If I was you I would talk to a local mercury/nercruiser main dealer and ask them and probably ask them to cheack the bonding of engines and legs.

 

[Jurgen]

I would have expected it to be zinc. I dont know a lot about mercruiser, what is the props stainless or aluminium?

If I was you I would talk to a local mercury/nercruiser main dealer and ask them and probably ask them to cheack the bonding of engines and legs.

Props are stainless, have Mercuryman poping down to do some work so will ask him the question re engine bonding

 

[birchwood330]

Bravo 2, keep the boat in seawater.

Notices that the Port Ram anodes had almost dissapeared whereas the stbd rams were untouched.

Also the small round anodes that sit @ the from of the drives where as new but the anodes @ the rear of the drives were nearly gone as well?????

This can be due to what you are berthed next to or what else is around you. Aluminum anodes are more effective and provide better protection than zinc anodes in both fresh and salt water . They are also now OEM fit for mercruiser drives. However they should not be mixed with zinc anodes, eg aluminum drive anodes with zinc trim tabs and vice-versa.

 

[VicS]

zinc usually is the prefered material however mercruiser had problems especially with the b3 with stainless props eating the anodes up too quickly & then starting on the drives so they started using alluminium to make them last longer

I assume its a poorer grade ally than the drives are made from

so you can use either but keep an eye on them as they can be gone in 12 weeks

They are a special alloy to a US military specification, or similar, which crucially contains a small percentage if indium

Their electrode potential is slightly more negative that zinc anodes making them a little more effective than zinc.

In brackish water zinc anodes may become passivated with a layer of oxide and rendered ineffective. Aluminium anodes remain effective in brackish water.

 

[Beamishken]

Bravo 2, keep the boat in seawater.

Notices that the Port Ram anodes had almost dissapeared whereas the stbd rams were untouched.

Also the small round anodes that sit @ the from of the drives where as new but the anodes @ the rear of the drives were nearly gone as well?????

check the little bonding wires to the rams & the ones at the bottom of the transom shield to the gimbal ring are all in tact on both drives if one is missing or not got a good connection that could explain the ram anodes being different

you can also get the mercathode tested although these seem to have a limited effect

also the rear round anodes will disapear faster due to you having stainless props on the bravo 2's on later bravo drives there are two anodes fitted above the props & another fitted to the center of the prop shaft

if you google bravo3 corrosion issues there was a lot of problems with them in the states I think there was talk of a class action due to the no of rotted drives

 

[Jurgen]

Will have a long think about all of the comments & advice then go to the pub and cry lol.

Still non the wiser but will look into some of the advice given, in particular will check the engine bonding & the wires @ the base of the rams!

Blooming boats!!! Lol

 

[Beamishken]

I wouldnt stress too much about it just try to keep the paintwork on the drives good & touch up any chips etc as soon as you can & check the anodes regularly even if it means getting your feet wet & changeing then in shallow water if you dont want to pay for a lift mid season still better then leaving them & letting the drives rot

I can reach the ram anodes & the rear round one on mine by trimming up & lying on the bathing platform if those are the ones that are corroding quickest then you might get two sets to one of the front ones

I also leave the shore power disconnected too as that accelerates the corrosion process but thats only practical if you can keep checking the boat regularly to ensure the bilge pumps arent flattening the battery

the corrosion issue is only a problem if you just put the boat in the water & forget about the drives

 

[Jurgen]

I wouldnt stress too much about it just try to keep the paintwork on the drives good & touch up any chips etc as soon as you can & check the anodes regularly even if it means getting your feet wet & changeing then in shallow water if you dont want to pay for a lift mid season still better then leaving them & letting the drives rot

I can reach the ram anodes & the rear round one on mine by trimming up & lying on the bathing platform if those are the ones that are corroding quickest then you might get two sets to one of the front ones

I also leave the shore power disconnected too as that accelerates the corrosion process but thats only practical if you can keep checking the boat regularly to ensure the bilge pumps arent flattening the battery

the corrosion issue is only a problem if you just put the boat in the water & forget about the drives

Luckily the boat is out of the water @ the moment so have taken off the rotten ones.

Have a galvanic isolator so have some protection for the boat. Just weird that 1 set of Ram anodes rot and the others don't???