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Should this anode be replaced? (pic)

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Should this anode be replaced? (pic)

Old 03-15-2019, 04:22 PM
  #21  
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at 2.5 years old and 800 hours of usage, i would be replacing!

Last edited by mystery; 03-15-2019 at 06:31 PM.
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Old 03-15-2019, 05:01 PM
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Old 03-15-2019, 05:14 PM
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Default Conductivity test

There is zero conductivity across the surface of the old used trim tab anode (first picture above) even with the probes an inch apart and pushed hard against the surface. But after the vinegar bath, the bracket anode has perfect conductivity.

The anodes get that brown surface very quickly. My maintenance log shows that I first replaced them at 152 hours because they looked like that. I guess my 100 service will now include removing and soaking the external anodes.
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Old 03-15-2019, 08:25 PM
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Your trim bracket anode is made out of zinc and is not protecting your engine. The trim anode is made out of aluminum and it is working overtime. The motor manufacturers always install aluminum anodes at every position because they know zinc is not reactive enough to protect engines.
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Old 03-16-2019, 03:31 AM
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I would replace all with known new materials. I agree that they look like different metals.
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Old 03-16-2019, 04:24 AM
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as mentioned, Yamaha branded anodes - factory/spare parts - are "aluminum" - only.
aftermarket anodes are also available in "zinc" (why, I can't fathom)

If in fact the bracket anode is zinc,
then as mentioned, the aluminum skeg anode will protect it as well,
and will be doing "all the work"

Its easy enough to determine if the bracket anode is "zinc" or "aluminum" - weigh it:
(actually one ought to be able to discern just from the 'heft" - the delta is >2x)

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Last edited by Fwpratt; 03-16-2019 at 01:58 PM.
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Old 03-16-2019, 01:49 PM
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It looked like there was a lot of corrosion around the bolt holes. That’s why I meantioned cleaning up the mating surfaces, sand them to clean metal to metal ,so that the bolts are not the only conductive path.
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Old 03-17-2019, 02:07 AM
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My used bracket anode weighs 1.945 lbs, so it's zinc. I think I remember hearing my mechanic say that the motor comes with an aluminum anode for both fresh and salt water, but that zinc is best for salt water? At boatzincs.com, they say "These Mil-Spec zinc anodes provide excellent corrosion protection for Yamaha outboards operating in salt water." Another source says "Three alloys available - Use Zinc (Martyr I) for salt water, Aluminum (Martyr II) for brackish water, or Magnesium (Martyr III) in fresh water."
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Old 03-17-2019, 07:01 AM
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Originally Posted by dove72 View Post
My used bracket anode weighs 1.945 lbs, so it's zinc. I think I remember hearing my mechanic say that the motor comes with an aluminum anode for both fresh and salt water, but that zinc is best for salt water? At boatzincs.com, they say "These Mil-Spec zinc anodes provide excellent corrosion protection for Yamaha outboards operating in salt water." Another source says "Three alloys available - Use Zinc (Martyr I) for salt water, Aluminum (Martyr II) for brackish water, or Magnesium (Martyr III) in fresh water."
Dont mix and match anode types. Stick to all zinc or all anode. FWIW, I was in 'brackish' water for most of my boating life. I always paid $$$ to switch everything to aluminum when I got a new boat. My current boat has two dozen or so anodes. Since I knew there was extensive recent analysis of the water for a possible dredging, I requested the results from the USACE and low and behold the salinity content was so high it might as well be called salt water and not brackish water. Fresh water can be seen at the surface but the deeper you go its pretty much salt. At 2-3' draft where most anodes are, it made sense to leave everything as zinc.
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Old 03-17-2019, 08:41 AM
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Originally Posted by dove72 View Post
My used bracket anode weighs 1.945 lbs, so it's zinc. I think I remember hearing my mechanic say that the motor comes with an aluminum anode for both fresh and salt water, but that zinc is best for salt water? At boatzincs.com, they say "These Mil-Spec zinc anodes provide excellent corrosion protection for Yamaha outboards operating in salt water." Another source says "Three alloys available - Use Zinc (Martyr I) for salt water, Aluminum (Martyr II) for brackish water, or Magnesium (Martyr III) in fresh water."
On this point boatzincs.com is wrong. I have a shop where we do bottom jobs on trailerable boats (almost all jobs are outboard boats or I/O's). In the process we remove all the anodes and replace most of them with new. I can say unequivocally that every boat that has been equipped with zinc anodes on the engines have some issues related to corrosion (frozen bolts, galvanic pitting of the castings, leaking trim hydraulics, etc.). Additionally, in these cases the zinc anodes are typically in great shape (which means they have not been doing anything) and invariably, when I point this out to the client they tell me something like "yeah, the guy at west marine told me they would last a lot longer than the factory ones so I bought these". The info at boatzincs and the knowledge at most marine stores is dead wrong and they are doing everyone a disservice by selling zinc anodes for outboards and I/O's. Always use aluminum anodes on these engines. Aluminum anodes are alloyed with other elements to make them sufficiently sacrificial when attached to aluminum engines and aluminum boat hulls. Zinc anodes will let your engines rot.

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Old 03-17-2019, 11:18 AM
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That bracket anode isn't doing its job, or else it isn't submerged. Honestly, I would expect to see way more wear on both of them after 2.5 years. Perhaps your wear is low because they're tilted free of the water when not in use? I replace mine after 3 months in the water, and I'm in a relatively low wear area with brackish water and no stray current. Are you using zinc anodes or aluminum? If your water is at all brackish or you ever go between fresh and salt water, you should be using aluminum. They don't last as long, but that's because they work better.
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Old 03-17-2019, 11:41 AM
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Thanks for all the information and suggestions. Just to summarize and clarify: The boat is kept on a lift but the bracket anode, which is zinc, has spent 850 engine hours running offshore in the Gulf over the last 2.5 years and many more hours sitting on anchor while fishing except for a 20 minute cruise in brackish water each way getting to and from the Gulf. The anode is touching the water when the boat is at rest but not at speed. After maybe 100 hours, the anode gets a brown coating and had no electrical conductivity across its surface when measured. After soaking in 50% vinegar, it is now clean and perfectly conductive. So my theory at this point is that it works for maybe 100 hours until it gets the brown coating, then doesn't work because it can't conduct. If that is the case, then the solution is to clean or replace it every 100 hours or possibly try the aluminum version. By the way, the engine doesn't show any obvious pitting or corrosion.
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Old 03-17-2019, 09:20 PM
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Originally Posted by Chaps View Post
On this point boatzincs.com is wrong. I have a shop where we do bottom jobs on trailerable boats (almost all jobs are outboard boats or I/O's). In the process we remove all the anodes and replace most of them with new. I can say unequivocally that every boat that has been equipped with zinc anodes on the engines have some issues related to corrosion (frozen bolts, galvanic pitting of the castings, leaking trim hydraulics, etc.). Additionally, in these cases the zinc anodes are typically in great shape (which means they have not been doing anything) and invariably, when I point this out to the client they tell me something like "yeah, the guy at west marine told me they would last a lot longer than the factory ones so I bought these". The info at boatzincs and the knowledge at most marine stores is dead wrong and they are doing everyone a disservice by selling zinc anodes for outboards and I/O's. Always use aluminum anodes on these engines. Aluminum anodes are alloyed with other elements to make them sufficiently sacrificial when attached to aluminum engines and aluminum boat hulls. Zinc anodes will let your engines rot.
Yup, just found this out the hard way and ordered aluminum anodes to replace the zincs.
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Old 03-18-2019, 12:30 AM
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Originally Posted by mystery View Post
at 2.5 years old and 800 hours of usage, i would be replacing!
So is that a solid value for saltwater? I have had my engine for ten years but no where near that many hours.
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Old 03-18-2019, 02:33 AM
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Is it OK to mix anode types like having a zinc trim tab anode since it wears quickly with water rushing against it but having an aluminum bracket anode? I assume you can mix them since the internal engine anodes seem to last a long time and must be at least as noble as zinc.

Also, at least for me, there's that brown coating in the picture that prevents the anode from conducting. I remember at 150 hours when my mechanic originally changed from the factory aluminum anode to a zinc one, the aluminum had no wear at all but he said it was no longer effective because of the coating. So if you're not observing wear on your anodes, I would test them by putting the probes of an ohmmeter on their surface.
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