Zincs and Anodes

Heyspike

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#1
Can someone school me on the ZIncs and Anodes on my Seafarer. Yahama 225.
The only thing I see is the one under the tilt/trim on the transom.

Also while we're at it, which hole in the motor does the speedometer readings?

Thanks,
John
 

DennisG01

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#2
First, they are ALL called sacrificial anodes - or just anodes. They can be made out of zinc, aluminum or magnesium. The most commonly used would be aluminum.

There is another one under the tail end of the anti-ventilation plate (above the prop). You would also have small ones in the heads - at the bottom - using a single bolt as a retainer.

The pitot (speedometer pickup) is on the leading edge of the lower unit, directly above the gear casing.

EDIT: click on the SIM Yamaha banner and look at the parts diagrams for your motor. That will show locations - good people there if you want to order from them, as well.
 
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Heyspike

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#3
First, they are ALL called sacrificial anodes - or just anodes. They can be made out of zinc, aluminum or magnesium. The most commonly used would be aluminum.

There is another one under the tail end of the anti-ventilation plate (above the prop). You would also have small ones in the heads - at the bottom - using a single bolt as a retainer.

The pitot (speedometer pickup) is on the leading edge of the lower unit, directly above the gear casing.

EDIT: click on the SIM Yamaha banner and look at the parts diagrams for your motor. That will show locations - good people there if you want to order from them, as well.
Do you replace the anodes on the bottom of the head regularly?
 

DennisG01

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#4
"Regularly" is a very relative term. It depends on use (hours) and the waters that the boat is in. Your location shows that you are in primarily fresh water? In general, fresh is less active than salt.
 

Doc Stressor

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#5
There are also internal engine anodes that need to be checked and/or replaced every few years if you are running in saltwater. Some are easily accessed and others require the heads to be removed. You can find the parts for your engine on the SIM Yamaha site.
 

Fishtales

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#6
Every couple years or so, sooner if you see them really getting bad. I'm told aluminum is good for both fresh and saltwater. Zinc for salt and magnesium for fresh. I go with zinc.
 

Shannon C.

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#7
There are also internal engine anodes that need to be checked and/or replaced every few years if you are running in saltwater. Some are easily accessed and others require the heads to be removed. You can find the parts for your engine on the SIM Yamaha site.
Where are these internal anodes you speak of?
 

Shannon C.

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#8
Sorry Doc, after reading the rest of your post I see you explained where they are, I was not familiar with those. At what time frame do you think they need to be replaced? I’m at 1500hrs.
 

seasick

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#9
Every couple years or so, sooner if you see them really getting bad. I'm told aluminum is good for both fresh and saltwater. Zinc for salt and magnesium for fresh. I go with zinc.
Zink is most effective in saltwater, aluminum is less effective but OK in general. No zinc in fresh water. If you do, they may last forever while your motor corrodes away:)
For some odd reason, at my marine supply house, zinc is easily found for my Yami but I only find aluminum for my Mercs. Mercury does recommend aluminum. There is more surface spot corrosion on the Mercs, almost none on the Yami and those motors are twice as old. I really don't know if the corrosion a result of the aluminum or just the quality of the Mercury products. I don't have enough data for that determination.
 

DennisG01

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Just a clarification on that Seasick... I think someone at the supply house gave you mixed up information. I work at a Mercury dealership... zinc used to be the material of choice, but most manufacturer's, if not all, have switched to aluminum (and that switch was actually many years ago, now). This includes Merc - the Merc brand anode is aluminum, not zinc. They are also generally considered a very good anode - as well as Yamaha's - also a good formulation of aluminum anode. In my opinion, there's a company called Performance Metals that makes an even better product than Merc or Yamaha - and they make it themselves here in the USA, rather than an engine manufacturer having it made for them.

There are, in my opinion, two main points when it comes to anodes. First, don't buy from some cheapo online place - there is definitely a difference in quality. Second, and maybe the most important, buy the type (Zn/Mg/Al) of anode that is working well for others in YOUR waters that have a similar setup to you, not from what you might find recommended on some forum.
 

Doc Stressor

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#11
Where are these internal anodes you speak of?


The easy ones are between your spark plugs in each cylinder bank. There are a total of 4. These are supposed to be checked every 200 hr or once a year. Easy is a relative term. I pulled a set out after 500 hr and ending up breaking one bolt and destroying one of the mounts. If you don't check them frequently with saltwater use they can get really welded in. Hit the bolts with PB blaster overnight and maybe apply some heat if they don't come right out. After removing the bolts, you need to twist the mounts to pull out the anodes. There is a rubber gasket that will probably be destroyed and should be replaced in any case. I used Corrosion X and then grabbed the mounts with pliers and rocked and twisted the anodes out.

There are additional internal anodes on the exhaust cover, cooling water passage, and rectifier cover that are to be inspected every 5 years or 1000 hr. This requires a lot of disassembly. I have not ever done this myself.
 

seasick

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#12
Just a clarification on that Seasick... I think someone at the supply house gave you mixed up information. I work at a Mercury dealership... zinc used to be the material of choice, but most manufacturer's, if not all, have switched to aluminum (and that switch was actually many years ago, now). This includes Merc - the Merc brand anode is aluminum, not zinc. They are also generally considered a very good anode - as well as Yamaha's - also a good formulation of aluminum anode. In my opinion, there's a company called Performance Metals that makes an even better product than Merc or Yamaha - and they make it themselves here in the USA, rather than an engine manufacturer having it made for them.

There are, in my opinion, two main points when it comes to anodes. First, don't buy from some cheapo online place - there is definitely a difference in quality. Second, and maybe the most important, buy the type (Zn/Mg/Al) of anode that is working well for others in YOUR waters that have a similar setup to you, not from what you might find recommended on some forum.
Thanks,
I think I am 'clarified' now.
 

DennisG01

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#13
Doc, I don't have anywhere near that many anodes (at least not that I'm aware of). On the engine block, I only have one on each cylinder head area. Meaning, two in total. I'm not aware of anything else. I would assume that the OP's engine would be the same as mine.

Unless... we don't know if the OP's engine is a 2-stroke or 4-stroke. Maybe that's the difference that you speak of? The 4-strokes have more?

John... what kind of engine/year do you have?
 

Doc Stressor

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#14
If I recall, you should have 2 anodes at the bottom of each cylinder head on a 250 OX66. They are long skinny things that are very different from the F2xx series. You may want to call up the parts diagram.

I just searched this up on THT:

Yamaha 250 HP OX66 Internal Anode Replacement
 
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