Stern Drive Anode

upnorth · 03-25-2008, 01:07 PM

I noticed the tiniest bit of oxidation on my boat's stern drive and my neighbor recommended I install an anode (and I've since learned that it ought to be a magnesium anode). I'm not certain what to do or where to install it/what style to get. The sterndrive is Volvo-Penta with an aluminum prop. Thoughts?

Blue Thunder · 03-25-2008, 02:20 PM

Quote:

Originally Posted by upnorth

I noticed the tiniest bit of oxidation on my boat's stern drive and my neighbor recommended I install an anode (and I've since learned that it ought to be a magnesium anode). I'm not certain what to do or where to install it/what style to get. The sterndrive is Volvo-Penta with an aluminum prop. Thoughts?

If it's a Volvo it should already have some type of anode on it. The problem is Volvo ships all of their drives, regardless of where they are going with salt water anodes. I, and most of us, I would assume, use our boats in fresh water only or at least most of the time. My Volvo DP drive (2000 Four Winns)pitted significantly before I could research the problem and you're right, you want magnesium not zinc for fresh water.

Blue Thunder

codeman671 · 03-25-2008, 02:39 PM

You are correct on magnesium. Zinc tends to corrode on the outside and scale over instead of dissolving in a uniform manner. Magnesium is a much better choice. I think with the more rapid rate of electrolysis in salt water the zinc does not have time to scale and works just fine.

GWC... · 03-25-2008, 02:48 PM

Review the reply that starts, "This is from boatzincs.com"

http://www.boatered.com/forum/topic.asp?TOPIC_ID=112161

TomC · 03-25-2008, 03:16 PM

I have more experience with Mercruisers than VP, but I wanted to point out that you likely have several anodes (4-6) on the outdrive - the discussion here implies there is just one, which is likely not the case.

All of them need to be changed over to magnesium for fresh water use - they each protect different sections of the upper and lower drive assemblies...

Phantom · 03-26-2008, 08:02 AM

Quote:

Originally Posted by upnorth

I'm not certain what to do or where to install it/what style to get. The sterndrive is Volvo-Penta with an aluminum prop. Thoughts?

Perhaps this will help !!

http://www.boatzincs.com/volvo_penta-magnesium.html

And for those of you with MerCruiser -- and wonder where the annodes are ........... This gives a great pictorial

http://www.boatzincs.com/bravo3-mag-kit.html for Bravo 3

http://www.boatzincs.com/alpha-one-gen2-mag-kit.html For Alpha 1

Grady223 · 03-26-2008, 11:20 AM

Do you need anodes on outboards, too? I have a Merc and a Yamaha. Never noticed if they have them.

Dave R · 03-26-2008, 12:50 PM

Quote:

Originally Posted by Grady223

Do you need anodes on outboards, too? I have a Merc and a Yamaha. Never noticed if they have them.

I would fully expect anodes on your lower unit. Any time there's two or more types of metal in the water, the least noble of metals will dissolve through electrolosis. Anodes are less noble than the rest of the lower unit, so they dissolve first. If you tilt the the thing out of the water whenever it's at rest, the anodes will last years in our water.

Phantom · 03-27-2008, 08:11 AM

Grady -- I would be SHOCKED

if your outboards lower unit did not have them.

On the Merc, look at the under side of the Cavitation plate (above the prop).

Nauset · 03-27-2008, 09:33 AM

Quote:

Originally Posted by upnorth

I noticed the tiniest bit of oxidation on my boat's stern drive and my neighbor recommended I install an anode (and I've since learned that it ought to be a magnesium anode). I'm not certain what to do or where to install it/what style to get. The sterndrive is Volvo-Penta with an aluminum prop. Thoughts?

What year & model of VP do you have? I have a 2000 DP-S which has two anodes. You should definitely go with mag anodes. Don't waste your time with Boatzincs.com, I tried to get mag anodes from them last year and got the run-around. Go see Charlie at Thurston's Marina Parts Dept. He got them for me in a week.

jayp603 · 05-03-2008, 07:55 PM

what type they are? how do i tell if my alpha 1 has salt or fresh water anodes?

chunt · 05-03-2008, 09:23 PM

bravo 3 drives use an aluminum anode. The idea being, the bare anode will carode before the painted i/o.

Dave R · 05-04-2008, 10:38 AM

Quote:

Originally Posted by chunt

bravo 3 drives use an aluminum anode. The idea being, the bare anode will carode before the painted i/o.

I took the aluminum anodes off mine and put on magnesium.

03-25-2008, 01:07 PM	#1
upnorth Senior Member Join Date: Jan 2005 Posts: 64 Thanks: 0 Thanked 2 Times in 2 Posts	Stern Drive Anode I noticed the tiniest bit of oxidation on my boat's stern drive and my neighbor recommended I install an anode (and I've since learned that it ought to be a magnesium anode). I'm not certain what to do or where to install it/what style to get. The sterndrive is Volvo-Penta with an aluminum prop. Thoughts?

03-25-2008, 02:48 PM	#4
GWC... Senior Member Join Date: Apr 2004 Posts: 1,325 Thanks: 5 Thanked 0 Times in 0 Posts	Review the reply that starts, "This is from boatzincs.com" http://www.boatered.com/forum/topic.asp?TOPIC_ID=112161 __________________ [Assume funny, clever sig is here. Laugh and reflect... ]

03-25-2008, 03:16 PM	#5
TomC Senior Member Join Date: Apr 2004 Location: Lakes Region Posts: 707 Thanks: 25 Thanked 106 Times in 72 Posts	more than one anode I have more experience with Mercruisers than VP, but I wanted to point out that you likely have several anodes (4-6) on the outdrive - the discussion here implies there is just one, which is likely not the case. All of them need to be changed over to magnesium for fresh water use - they each protect different sections of the upper and lower drive assemblies...

03-27-2008, 08:11 AM	#9
Phantom Senior Member Join Date: Jul 2005 Location: Berlin, Ma / Gilford Posts: 1,934 Thanks: 450 Thanked 605 Times in 341 Posts	Grady -- I would be SHOCKED if your outboards lower unit did not have them. On the Merc, look at the under side of the Cavitation plate (above the prop). __________________ *A bad day on the Big Lake (although I've never had one) - Still beats a day at the office!!*

05-03-2008, 07:55 PM	#11
jayp603 Senior Member Join Date: Feb 2008 Posts: 50 Thanks: 3 Thanked 5 Times in 2 Posts	can u tell by looking? what type they are? how do i tell if my alpha 1 has salt or fresh water anodes?

03-25-2008, 02:39 PM	#3
codeman671 Senior Member Join Date: Jan 2005 Posts: 3,516 Thanks: 221 Thanked 821 Times in 493 Posts	You are correct on magnesium. Zinc tends to corrode on the outside and scale over instead of dissolving in a uniform manner. Magnesium is a much better choice. I think with the more rapid rate of electrolysis in salt water the zinc does not have time to scale and works just fine.

03-26-2008, 11:20 AM	#7
Grady223 Senior Member Join Date: Apr 2004 Location: New Hope, PA & Barndoor Island Posts: 465 Thanks: 93 Thanked 24 Times in 18 Posts	Do you need anodes on outboards, too? I have a Merc and a Yamaha. Never noticed if they have them.

05-03-2008, 09:23 PM	#12
chunt Member Join Date: Jan 2005 Posts: 20 Thanks: 0 Thanked 0 Times in 0 Posts	bravo 3 drives use an aluminum anode. The idea being, the bare anode will carode before the painted i/o.