zinc

[Pony]

What can happen the peice of zinc that goes on the motor is missing??....i see the bolt holes where it is supposed to go on my 25hp johnny. previous owner removed it because its in the way of the hydrofoil that was added.<br /><br />Seems like a stupid question i know, but if i really need it i am gonna try to find a new one. I posted it here because im not sure its engine specific because it can be mounted on the transom right??

 

[05GlastronSX]

Re: zinc

it sounds like you lost one of your corrosion anodes. no big deal..just go buy a replacement a bolt it back on and youll be good to go.

 

[Pony]

Re: zinc

Is it more of an issue in saltwater, or is in critical in fresh water as well?

 

[Heller1]

Re: zinc

If your motor is left in the water, under the right circumstances, you will have ALOT of pitting and eating away of your motor and prop. We lost one on our 75 merc early in the summer and didnt notice till last week, the prop was unsuable, i could literally break the fins off like breaking a cracker...the motor is all pitted now...be careful

 

[umblecumbuz]

Re: zinc

If you want to fit a sacrificial anode and the hydrofoil is still in the way, drill a hole elsewhere and screw it on there, or mount it on top of the foil using a longer bolt.<br /><br />Always good insurance to have good zincs.

 

[Pony]

Re: zinc

Well im definately gonna get one, or at least try to find the one that was removed. I thought i saw it when i was going through stuff when i bought the boat.....<br /><br />How long would a motor have to sit in the water?? I doubt i have had a zinc on it in all the times i have used it, but i havent left it in the water yet either.....but when i go up north it will be in there for at least a week.

 

[umblecumbuz]

Re: zinc

Fresh water? Probably no problem, but wise.<br />Salt? you need a zinc.<br /><br />Either way, they're not expensive. Look upon the cost as insurance.

 

[Jdeagro]

Re: zinc

It is important to understand that water is a conductor of electricity, and will cause electrolysis. Electrolysis is a corrosion of the metal. It simply dissolve. Salt water chemicals make it more corrosive than fresh water, however it is not uncommon to see similar levels of corrosion in fresh water. Some areas of slat water are more corrosive than other. <br /><br />The use of sacrificial anodes is wise under and circumstances. What happens? The anodes are lower grade metal than the other parts which you are attempting to protect (called "least noble" metal). The electrical current is drawn to these metals first, and they will dissolve first. By using them and maintaining them, you avoid the corrosion of the other parts.

 

[Pony]

Re: zinc

Thanks guys, lots of helpful information. good to know these things.

 

[Ralph 123]

Re: zinc

Pony, Zinc is for saltwater - you need Magnesium for freshwater.<br /><br /><br />

Zinc will not work in fresh water it is purely for salt. Magnesium is the simple answer to your problem with fresh water, although magnesium needs to be removed when going into salt water for long periods.

http://www.finishing.com/83/90.shtml

 

[Scaaty]

Re: zinc

All the time in the water..yes. Month at a time...maybe. Week....spend the money on gas. Outboard? Just tilt it out of the water

 

[umblecumbuz]

Re: zinc

Quoted from Ralph's post:<br />Zinc will not work in fresh water it is purely for salt. Magnesium is the simple answer to your problem with fresh water

This is oversimplifying the situation, and needs to be read with caution!<br /><br />There is very rarely such a thing as pure 'fresh' water. Even lake or river water which is not considered salty often has dissolved solids that will increase the rate of galvanic corrosion. Such water may eat magnesium anodes for breakfast. The temperature, clarity and rate of flow of the water also has a bearing on its corrosive potential.<br /><br />Mag anodes are made to dissolve faster than zinc anodes, which is why they are not recommended for salt water. They should be used in 'gentler' conditions where zinc anodes do not offer sufficient protection. <br /><br />If a boat is trailered and 'dipped' then the absence of anodes is not so important as if it was left in the water. Often the safest way is to seek local knowledge - from other boat owners, the local marina or chandlery store.<br /><br />Considering the cost of correct anodic protection compared with the cost of repairing a corroded leg or prop, then it pays to get it right.

 

[Pony]

Re: zinc

thanks stillfishing and ralph-<br /><br />Man this is much more complex than i thought it would be. My motor never has and never will see salt water. The thing that doesnt make sense is that the majority of motors i would guess are used in freshwater. especially around the here in the midwest.....if zinc "is" only for salt water, then why not put magnesium anodes on the motor out of the factory?

 

[Dunaruna]

Re: zinc

Totally agree with Stillfishing.<br /><br />

Originally posted by pony85:<br /> thanks stillfishing and ralph-<br /><br />if zinc "is" only for salt water, then why not put magnesium anodes on the motor out of the factory?

I'll try and reword something that stillfishing said - Water does not conduct, it is the impurites in water that are the catalyst for galvanic corrosion. Impurties such as salt & minerals. Not all fresh water is the same, different lakes/rivers contain different concentrations of minerals. Therfore - magnesium does not always suit, to make things even more complicated, there are different types of magnesium and zinc anodes.<br /><br />The first thing to do is check with your motor manufacturer for recommendations, then seek local knowledge - local marinas are the best place to ask about anodes.<br /><br />Aldo

 

[Pony]

Re: zinc

aldo, thanks for clarifying...i will talk to the guys at the local marina and see what they recomend...you guys are great, thanks for bearing with me as i learn

 

[Ralph 123]

Re: zinc

Water type is the final influential factor when choosing an anode. When used in freshwater, a zinc anode forms a coating of zinc hydroxide that insulates it and stops it from working.

http://www.gulffishing.com/tips_anode.html <br /><br />Magnesium for fresh water. Zinc for salt...<br /><br />

The type of water you'll be boating in -- and the combination of metal found on your boat -- determines the type of sacrificial anode you will need. For freshwater boating, chances are you'll need magnesium or aluminum alloy anodes. Zinc will not protect anything in fresh water because there it has a potential of about 900 milliamps; whereas, a magnesium in freshwater will have the 200 milliamp spread needed. In saltwater, zinc will have a potential of about 1200 milliamps. -- shipshape TV

http://www.diynetwork.com/diy/bo_maintenance_repair/article/0,2021,DIY_13718_2278043,00.html <br /><br />Magnesium for freshwater Zinc for saltwater<br /><br />

These sacrificial anodes are designed to protect outboards or outdrives in freshwater lakes and rivers. Their use in salt or brackish water may result in accelerated corrosion, leaving your engine with little or no protection. <br />Magnesium anodes are your best choice for fighting corrosion problems caused by stray current or pollution in freshwater. Magnesium is very active in freshwater and will protect your engine parts much more effectively than zinc.<br />

Magnesium for freshwater Zinc for salt

 

[Dunaruna]

Re: zinc

I'm sorry, but that website has too many holes in it's quotes.<br /><br />They do not account for temperature, they do not account for mountain lakes with high mineral content, they do not account for different types of outboard/sterndrive alloys, they do not account for different concentration of mag or zinc or alloy in the anode, they do not account all the little metal based additions we fit to boats, they do not account for shore power leakage or a generator ground leak.<br /><br />[Quote: "Magnesium for freshwater Zinc for salt".]<br /><br />That is just a generalisation. I understand that the authors have degrees and doctorates, but they do not account for the real world.

 

[SCO]

Re: zinc

If Ralph says the zinc will passivate itself in fresh, I'd say put a mag on it if they make them( I only know salt water stuff). Magnesium is more anodic than zinc so it ought to work better anyway. If you cant find one use a zinc and scrape it off now and then if you want. My experience tells me that galvanic corrosion is not much of a problem in fresh water with trailered boats. I bought a 25 year old fresh only aluminum motor that looked practically new, no corrosion , compared with any typical salt water run motor, and it didn't have any zincs. I put some on it and it corroded more in 2 years of salt service than the previous 25(mind you it didn't corrode badly at all, just from none to some). I don't think the corrosion I got was galvanic corrosion, just plain corrosion. Aluminum is one of the most corrosive metals but it is also self passivating, forms a protective oxidation shield that insulates it. Stray currents, bad battery hookups, that kind of thing is what can get you and that probably will not be a factor, but look at it as Dunaruna notes. Bad design causes it too. Area considerations...an aluminum plate with SS rivits is ok, but if you were to have a ss plate with aluminum rivets, it would eat those rivits up. The rivets would be sacrificial anodes and the big ss area would draw electrons from the rivits and accelerate the corrosion. In big equipment, pipelines , oil rigs, they set up electric currents to protect the metals...but nobody does that for typical outboard motor apps.

 

[umblecumbuz]

Re: zinc

Agree with Dunaruna.<br /><br />To simply parrot another's generalization is to ask for trouble.<br /><br />Check with the locals who've been boating for years. They'll know.<br /><br />Epictetus also said: First learn the meaning of what you say, and then speak.

 

[SCO]

Re: zinc

Who's the parrot, me? No parrot here if that's what you mean. I took a bonified course on it, still have the book, and just skimmed Ralphs post. Pony was concerned about his motor cause it didn't have a zinc on it. Probably isn't hurt, but if it is, water over the dam. What other option is there but to put on an anode? Why not Magnesium? Were it up to me, i'd just put on a zinc unless a magnesium was right there at the boat store. This isn't worth much worry.