Can a zinc anode be added to an older outboard?

[Todd in NY]

My 1973 Evinrude doesn't have a zinc anode on it. The previous owner added electric start to it and I am wondering if the motor is grounding itself into the water when it is hooked up to the battery. The motor is used on a 1974 utility boat that does not have a fuse block. The electronics that I use on that boat are wired directly to the battery with inline fuses on the positive side. I haven't hooked the motor up to the battery because I don't want to turn the motor or boat into a giant sacrificial anode, so I leave the wires covered and disconnected and use the rope start to start the motor. I also don't know if he installed any parts that would allow the motor to charge the battery, or if he just installed the starter parts. Any thoughts or ideas would be greatly appreciated.

 

[Chas0218]

The electric start should be grounded to the battery only not to your boat.

[Xxx]

Like what Chas said, I highly doubt there is a charge system, lots of those older engines were drilled for a starter. I have a older 25hp Merc. That's supposedly use 40:1 oil mix that's how old it is and I put a starter on, it didn't have a charging system. It should be grounded to the battery and that's it. All grounds should be isolated from the structure of the boat.

[Todd in NY]

Ok, thanks! I doubt he put a charging system on it, and the starter is wired directly to the battery. I just wasn't sure if that created any kind of current through the motor and into the water. It's the boat and motor I bought last November on black Friday and it runs like a champ. I had a local shop rebuild the carb and change the water pump on it before I ran it. The only thing I don't like about the motor is that is doesn't have the tell-tale to tell me that she's pumping good water.

 

None of the electronics are grounded to the boat, so I should be good.

Edited February 3, 2016 by Todd in NY

[Chas0218]

I doubt it would pull any extra current only because the solenoid isn't always running making contact with the relay.

[Chas0218]

You should see water coming out the port at the back of the mid section motor housing.

Edited February 3, 2016 by Chas0218

[Frogger]

Just a thought, isn't the starter grounded to the block which In turn would ground the hull /boat ? Remember it's not just stray current that causes galvanic corrosion it can be two different metals on the nobility table that can start corroding in water hense why we have zincs on the outboards etc. if your not keeping it in the water or trailering it maybe it's not a worry. I might check it though with an ohm meter to make sure you .6-.7 Just an opinion.

[Todd in NY]

I'd have to check, but I believe it's grounded to the block. I always trailer the boat.

This galvanic corrosion idea popped into my head because the off season gives me too much time for random thoughts.

[rolmops]

Electrolysis mostly happens in salt water or on docks that have boats hooked into shore power. If you have your boat on a trailer you really do not have to worry about any of that stuff.

[TileMan Dan]

What rolmops said.

[Todd in NY]

Thanks for the feedback. My 15hp kicker and my 90hp main motor on my 19ft Sea Nymph both have anodes on them, so I figured I'd ask the question. Rather be safe than sorry, and maybe someone else had the same question and never asked.

[Prof T]

If you are running in fresh water only, you might want to consider switching over to magnesium anodes instead of the zinc. They won't last as long, but I think that's what you want.

 

My boats, a 26 Wellcraft IO and a 19 Sea Nymph outboard sit at an iron pipe dock for about 5 months a season. I got concerned because I saw very little disintegration of the anodes. In fact, neither had ever needed replacing. A buddy who had some issues with his outdrives did some research and found that magnesium was a better sacrificial material.

 

I switched out the Wellcraft last season and now see a lot of pocking in the anode, reassuring me they are reacting to something. I plan to do the outboard this year.

 

Here's a source: boatzincs.com

[Todd in NY]

If you are running in fresh water only, you might want to consider switching over to magnesium anodes instead of the zinc. They won't last as long, but I think that's what you want.

 

My boats, a 26 Wellcraft IO and a 19 Sea Nymph outboard sit at an iron pipe dock for about 5 months a season. I got concerned because I saw very little disintegration of the anodes. In fact, neither had ever needed replacing. A buddy who had some issues with his outdrives did some research and found that magnesium was a better sacrificial material.

 

I switched out the Wellcraft last season and now see a lot of pocking in the anode, reassuring me they are reacting to something. I plan to do the outboard this year.

 

Here's a source: boatzincs.com

Thanks for the tip. I never would've thought about magnesium instead of zinc.

[lrg355]

If you look into zinc in fresh water, you will find they do not work well. It is rare to see them erode. Magnesium is best but there are aluminum types that work well also.

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[rolmops]

I do not want to start giving organic chemistry  sermons ,but  out of the three, zinc is the only ferrous metal alloy. the other two are non ferrous (not metal) Magnesium and aluminum have a very different ionic charge difference with water and magnesium by its very nature  decays faster.I am not so sure if aluminum does has any quality has an anode. At least magnesium and zinc do the same job equally good. The fact that magnesium  decays faster has to do with the character of the material and not with the quality of the job they do.

Edited February 6, 2016 by rolmops

[lost a lure]

Zinc is a pure non ferrous metal.

[rolmops]

Zinc is a pure non ferrous metal.

That is correct,but very often in the alloys being used a small quantity of iron is added to increase conductivity