Any DIY anodes for galvanic corrosion?

[The other Steve]

anybody ever hear of anyone making a sacrificial zinc setup on their boat for an onboard system? The marina didn't change my zincs, and they are shot. I wanted to not have to be without the boat for a few days, which would be the case of I left it off to them to do. I have twin mercruiser ma with alpha drives. Could I connect a wire to each block and put a zinc on the other end and chuck it overboard while sitting at the dock? Do I have to tie into the onboard electrical system? If so, the 12 V d/c or the 110 V a/c system?
thanks

[Southshorerob]

Just replace the zinc's yourself . If your unsure take them out off and run to the parts place and match them up and replace . Not hard job at all .

[DrBrianDDS]

Anodes themselves are not tied into electrical system. They rely on metal-on-metal contact to do their job. Usually you want them to touch bare metal of the places they are protecting. I wouldn't count on cheating with a wire. Shouldn't take that long to change. Do you have a trailer or need to be hauled? I'd say less than an hour job once she's out of the water. Unless you know a scuba diver.

[Parashooter]

Just replace the zinc's yourself . If your unsure take them out off and run to the parts place and match them up and replace . Not hard job at all .

No need - they sell a complete kit specifically for the Alpha drive (or beta etc.) You also need to get zincs for whatever else you may have, trim tabs, etc.

But it's not too difficult to do in water if you're comfortable in a mask.

Now - was the marina TOLD to change them? or told to prep it for summer? if they slacked off I'd have them getting it done on a "right now" out & in basis.

[T.J.]

Anodes themselves are not tied into electrical system. They rely on metal-on-metal contact to do their job. Usually you want them to touch bare metal of the places they are protecting. I wouldn't count on cheating with a wire. Shouldn't take that long to change. Do you have a trailer or need to be hauled? I'd say less than an hour job once she's out of the water. Unless you know a scuba diver.

^ ^ This...
They basically rely on metal to metal contact to protect from corrosion, and can also tap into the boats natural ground (negative)system. Just hanging a zinc over the side wired to the block will not protect all of the sterndrive's components.
Anytime 2 different metals make contact, and are also in salt water, they will discharge electrons like a battery. Adding a sacrificial zinc anode enables those electrons to come from the zinc rather than the metals you're trying to protect.
There are 4 zincs on the alpha drive. The zinc trim tab, 2 zinc buttons, and a zinc block under the gimble housing.All are usually very easy to replace, once you have access to the back of the boat.
Many who want to replace their own, with the boat in the water, will find a sandy beach to pull onto. Or if your boat is too big for that, anchor close to one with the stern in low water facing the beach, and gain access that way.

The two zinc buttons will just unscrew off of the housing, the zinc block under the gimbel has 2 bolts holding it on, and the zinc trim tab has a 3/8" hex bolt through the top of the cavitation plate.
Just note the position of the trim tab before removing it, and replace it at the same angle its now facing.. It also acts as a small rudder to compensate for the prop torque and should be set to help the boat steer straight.

[GettingFedUp]

^ ^ This...
They basically rely on metal to metal contact to protect from corrosion, and can also tap into the boats natural ground (negative)system. Just hanging a zinc over the side wired to the block will not protect all of the sterndrive's components.
Anytime 2 different metals make contact, and are also in salt water, they will discharge electrons like a battery. Adding a sacrificial zinc anode enables those electrons to come from the zinc rather than the metals you're trying to protect.
There are 4 zincs on the alpha drive. The zinc trim tab, 2 zinc buttons, and a zinc block under the gimble housing.All are usually very easy to replace, once you have access to the back of the boat.
Many who want to replace their own, with the boat in the water, will find a sandy beach to pull onto. Or if your boat is too big for that, anchor close to one with the stern in low water facing the beach, and gain access that way.

The two zinc buttons will just unscrew off of the housing, the zinc block under the gimbel has 2 bolts holding it on, and the zinc trim tab has a 3/8" hex bolt through the top of the cavitation plate.
Just note the position of the trim tab before removing it, and replace it at the same angle its now facing.. It also acts as a small rudder to compensate for the prop torque and should be set to help the boat steer straight.

Great post Terry. "Many who want to replace their own, with the boat in the water, will find a sandy beach to pull onto. Or if your boat is too big for that, anchor close to one with the stern in low water facing the beach, and gain access that way." Brilliant.

[The other Steve]

thanks for the graphic. thats the drive. The boat is 29 foot plus the 4 foot swim platform which covers the drives. i would need a mask, but the bottom at the dock is real soft mud, like quicksand almost. i told them to do it while it was out of the water to put a new motor in. i just put the drives in trailer mode to check last week and saw they didnt do it. they forgot, so i will push the issue to the top if i need to, and not pay any haul out charges.
thanks for your assistance.

[Sig]

The swim platform makes it more difficult to do in the water. If you can't get the marina to do it in the time frame you want, you could beach it onto a sandy beach on an ebb at midtide. I've seen some very frugal sailboaters do this to paint the bottom. Tide goes out, do the necessary work, tide comes back in & away you go. I'm not advising this, just saying it's another option.

[The other Steve]

There is no room to stand under the swim platform. I might be able to try it if the tide is right, standing up. I cant do it bending over under the platform. I will get a cheap Harbor Freight ratchet wrench, since it will be submerged in salt water. A mask and holding my breath might work. But there is such brown tide out there in peconic bay lately, the canal water looks like chocolate milk. very low visibility.