Is a little corrosion normal?

[KnotConnected]

Hey!

Some of ya'll may remember my ordeal last winter where I ended up replacing my entire Bravo3 lower unit due to corrosion on the inside. Since then I've replaced the anodes, and have fixed the ground wire circuit on the lower unit (multiple steel ground wires weren't connected)

Well, after a full summer of being in the slip, connected to shorepower AC at the marina, there seems to be a little corrosion on the (once-was) perfect lower unit (pics below)

Question being: Is this normal, or is this this indicative of a problem that could chew up my entire out drive after a year or so again?

http://i46.photobucket.com/albums/f117/n915aa/IMAG1197_zps3a0018a9.jpg

http://i46.photobucket.com/albums/f117/n915aa/IMAG1196_zps693bef69.jpg



thanks!

 

[thumpar]

Re: Is a little corrosion normal?

Are you boating in salt? My drive didn't have that much corrosion on it when I sold it last year and it was from 1983. We only boat in freshwater.

 

[gm280]

Re: Is a little corrosion normal?

Are you certain you don't still have a grounding problem. You stated you use shore power on the boat. Is there any grounding issues with the shore power circuits? If for some reason you have an isolated grounding or even a neutral power issue on the boat, it could be your problem. Check it out...

 

[Fleetwin]

Re: Is a little corrosion normal?

Many marinas can be very "Hot" in terms of stray electricity in the water.

I believe you may want to invest in a MerCathode system.

710-98869A14 MERCATHODE KIT - Mercury - iboats

 

[Thalasso]

Re: Is a little corrosion normal?

Do you have the Mercathode system on your boat? If so i can tell you how to check the system and how to double the field around the boat. The type of water makeup and flow of water will effect your protection if you have the Mercathode system.You can check your bonding wires/system with a multimeter to make sure they are bonded. Everything metal on your boat needs to be bonded somehow.

Mercruiser Mercathode Systems for galvanic corrosion ...
Mercruiser Mercathode Systems for galvanic corrosion protection

This is upside down. It would be mounted underneath the gimble housing. It will look like a heat sink.




The blue controller might be black on your boat beings it's older. It will be mounted on top of the engine in a inconspicuous place. You will have to look.

 

[bear_69cuda]

Re: Is a little corrosion normal?

I agree! ^^^^^^^^

MerCathode system...

 

[crabby captain john]

Re: Is a little corrosion normal?

One year old???? Only for a season? Not normal, not for a full year, forget a summer season~~~~ not in salt either.

 

[lg260ss]

Re: Is a little corrosion normal?

That is quite a bit of corrosion for a summer. I'm going to guess by your location in your sig. that you are in fresh water. I have 2 questions:
1) Where is your propshaft anode?
2) Are you using magnesium anodes?

If you have a new B3 lower unit then it should have a propshaft anode that goes over the rear prop nut. If you do not have a threaded hole for the anode in your propshaft, then you need to get the propshaft anode add-on kit that they make for the older B3 units. (which means that your "new" B3 is likely a rebuilt one from before 2004.
If you are in fresh water, you MUST use magnesium anodes to properly protect your drive, they should be OEM only, no knock-off brands. There are 5 total anodes in the kit and all need to be on the drive at all times. I also agree with others who have stated to check your Mercathode system. You can also add a second Mercathode to increase the protection.

 

[Thalasso]

Re: Is a little corrosion normal?

That is quite a bit of corrosion for a summer. I'm going to guess by your location in your sig. that you are in fresh water. I have 2 questions:
1) Where is your propshaft anode?
2) Are you using magnesium anodes?

If you have a new B3 lower unit then it should have a propshaft anode that goes over the rear prop nut. If you do not have a threaded hole for the anode in your propshaft, then you need to get the propshaft anode add-on kit that they make for the older B3 units. (which means that your "new" B3 is likely a rebuilt one from before 2004.
If you are in fresh water, you MUST use magnesium anodes to properly protect your drive, they should be OEM only, no knock-off brands. There are 5 total anodes in the kit and all need to be on the drive at all times. I also agree with others who have stated to check your Mercathode system. You can also add a second Mercathode to increase the protection.

Aluminum anodes are just as good. Merc puts them on as standard anodes. You don't need to add an additional Mercathode if you already have one. Adding another controller will do the same thing

 

[thumpar]

Re: Is a little corrosion normal?

Aluminum anodes are just as good. Merc puts them on as standard anodes. You don't need to add an additional Mercathode if you already have one. Adding another controller will do the same thing

The anode type depends on the water you boat in. In his situation magnesium is recommended.

 

[Thalasso]

Re: Is a little corrosion normal?

The anode type depends on the water you boat in. In his situation magnesium is recommended.

Mercury and Johnson/Evinrude/OMC started selling the aluminum anodes in the early 1990?s. Other manufacturers are switching to aluminum too.


http://www.performancemetals.com/images/anodes/ABYCrec.jpg

And

WHAT?S ALL THIS ABOUT ALUMINUM SACRIFICIAL ANODES
www.martyranodes.com/content/martyr-resources/Aluminum Anodes.pdf

Another point to consider in the choice is the
type of water
in which the boat will be used.
This can range from salt to
brackish to pure fresh water.
Some Hints
Don?t Mix Anode Types
. If you install different anode materials
like zinc and aluminum, the more active anode (aluminum) will
spend part of its effort protecting the less active metal (zinc). This
will reduce the overall protection that you are getting. A classic
mistake is adding a zinc transom anode to a Sterndrive equipped
with aluminum anodes. Transom anodes are connected through the
bonding system so make sure you install aluminum replacements.
Zinc in Freshwater
: In freshwater zinc can form a coating.
This quickly insulates the anode and stops it from working.
You may think your zinc anodes are lasting a long time when
in fact they have simply stopped working - stopped
protecting!
Keep an eye on your anodes
. When they get to half their original
size replace them. If you leave them any longer there may not be
enough surface area on the anode to deliver the protective current
you are looking for. Judging when to change your anodes can be
difficult!
Magnesium in Salt or Brackish water
: Magnesium is so
active that in salt water it can
disappear very quickly. If used
on an aluminum Sterndrive or
outboard motor it can be
positively dangerous. Aluminum
is ?amphoteric?, which just
means that you can ?overprotect? it. If you take your boat
down river to the ocean with
magnesium anodes you will
probably have a catastrophe on your hands. The
overprotection causes hydrogen
bubbles to form under the
paint on the drive resulting in the paint being blown off! You
also need to be careful about putting magnesium anodes on
an aluminum-hulled boat since
the same thing can happen.
Your freshwater may not be so fresh either. Acid rain and
general pollution can cause the water to be much more
conductive resulting in
the same problems.
Performance Metals has made life simple for the boat owner and
introduced the patented
Red Spot Wear Indicator
anode.
Performance Metals? range of aluminum alloy anodes have a Red
Spot plastic indicator that appears on the surface when it is time to
change.
Don?t forget - it?s better to spend a little on
replacing your anodes on
a regular basis than
the thousands you might incur buying new
propeller shafts or a new Sterndrive lower unit!
Aluminum - The Final Winner!
In our opinion the best all-round anode material is aluminum.
Consider these points !
?
Aluminum anodes are more active than zinc and are
accepted by the major Sterndrive manufacturers as
the best material to use.
?
Aluminum anodes are not so active that they are
dangerous in salt or brackish water as are
magnesium anodes.
?
Aluminum anodes will last
longer because of their
increased current capacity.
?
Aluminum is the only anode material that can be
used safely in all types of water.
?
Aluminum anodes are 2 ? times lighter than zinc
making them much easier to carry home from the
store!
?
Aluminum is a much better alternative than zinc as
far as the environment is concerned, since it is not
considered a pollutant.

 

[thumpar]

Re: Is a little corrosion normal?

Mercury and Johnson/Evinrude/OMC started selling the aluminum anodes in the early 1990’s. Other manufacturers are switching to aluminum too.


http://www.performancemetals.com/images/anodes/ABYCrec.jpg

And

WHAT’S ALL THIS ABOUT ALUMINUM SACRIFICIAL ANODES
www.martyranodes.com/content/martyr-resources/Aluminum Anodes.pdf

Mercury and OMC brands don't hang twin stainless props off their drives.

 

[lg260ss]

Re: Is a little corrosion normal?

Aluminum anodes are just as good. Merc puts them on as standard anodes. You don't need to add an additional Mercathode if you already have one. Adding another controller will do the same thing

Aluminum anodes are not as good in fresh water and whoever told you they are is wrong. Boat dealers and the customer are responsible for putting the correct anodes on the drive. Merc and Volvo (and others)ship their drives with Aluminum anodes because they do not know where the boat is going to be used (they ship to manufacturers) and aluminum can be used in all types of water. Both Merc and Volvo recommend magnesium in fresh water. Magnesium anodes in fresh water give you better protection because they are more active. Back in 2003 I bought a brand new boat. After the first season in clean, clear fresh water there was some corrosion on the drive. I cleaned up the drive, changed the anodes to magnesium and never saw any corrosion again.
If you trailer your boat, then aluminum is fine. But for boats that sit in the water for several months, magnesium is a must for all Bravo 3 and Volvo DPS drives, due to the large amounts of stainless steel on the drives.
Just because aluminum anodes last longer that Magnesium does not make them better in fresh water. Replacing anodes is part of the yearly maintenance of owning a sterndrive boat that is left in the water. If your anodes are not corroding enough to be replaced after a season in the water, then you are probably using the wrong anode. The anode is made to corrode, so your drive doesn't.
A merc Alpha or and Volvo SX drive is a different story and I would be fine with aluminum on either, unless I changed to a stainless prop at which time I would change the anodes to magnesium.

 

[Chris1956]

Re: Is a little corrosion normal?

There is definitely some stray current in the water. This current is usually caused by leakage from your boat or a neighbors boat, and diminishes over distance. You might check with some of your "slip neighbors" and see if you can find a pattern. If you can track it down to the boat that is leaking the current (including yours), you may be able to fix it.

 

[tpenfield]

Re: Is a little corrosion normal?

I do not see an anode on the propeller hub, so without that, you will continue to get corrosion in the areas that you showed in the pictures.

so, get the prop anode retrofit kit and check out the shore power / grounding stuff as mentioned.

 

[Thalasso]

Re: Is a little corrosion normal?

Mercury and OMC brands don't hang twin stainless props off their drives.

:facepalm:
Then what is that hanging off of the back of a Bravo111. Do some research rather then speak of something you apparently know nothing about.

 

[thumpar]

Re: Is a little corrosion normal?

:facepalm:
Then what is that hanging off of the back of a Bravo111. Do some research rather then speak of something you apparently know nothing about.

That is a Mercruiser. I know a little about them.

 

[Thalasso]

Re: Is a little corrosion normal?

Aluminum anodes are not as good in fresh water and whoever told you they are is wrong. Boat dealers and the customer are responsible for putting the correct anodes on the drive. Merc and Volvo (and others)ship their drives with Aluminum anodes because they do not know where the boat is going to be used (they ship to manufacturers) and aluminum can be used in all types of water. Both Merc and Volvo recommend magnesium in fresh water. Magnesium anodes in fresh water give you better protection because they are more active. Back in 2003 I bought a brand new boat. After the first season in clean, clear fresh water there was some corrosion on the drive. I cleaned up the drive, changed the anodes to magnesium and never saw any corrosion again.
If you trailer your boat, then aluminum is fine. But for boats that sit in the water for several months, magnesium is a must for all Bravo 3 and Volvo DPS drives, due to the large amounts of stainless steel on the drives.
Just because aluminum anodes last longer that Magnesium does not make them better in fresh water. Replacing anodes is part of the yearly maintenance of owning a sterndrive boat that is left in the water. If your anodes are not corroding enough to be replaced after a season in the water, then you are probably using the wrong anode. The anode is made to corrode, so your drive doesn't.
A merc Alpha or and Volvo SX drive is a different story and I would be fine with aluminum on either, unless I changed to a stainless prop at which time I would change the anodes to magnesium.

They have stainless.The only difference between the SX and the DPS is one has dual props. That's the only diff. Did you bother to look at or read the articles. I would think these people are a little more knowledgeable in the field then you or i. I didn't say i recommenced one over the other either. Look at the electrical scale diff between aluminum and Mag. there isn't much difference. .2 or 3 tenths

 

[Thalasso]

Re: Is a little corrosion normal?

That is a Mercruiser. I know a little about them.

And what company is Mercrusier? OMC not even in business. I guess they can't hang stainless off the back

 

[thumpar]

Re: Is a little corrosion normal?

Mercruiser is owned by Mercury but show me a Mercury OB with dual props hanging. The extra stainless changes things. If you want go do your research on what the factory recommends. For freshwater the only recommendation is MG with the b3. With the b2 and b1 AL is allowed but still MG is recommended.