Zinc Analysis

Boat has 135 Lehman.

It has two plate zinc's on the stern, one on prop shaft, two on bow thruster, one pencil zinc on heat exchanger.

I regularly find the zinc almost gone in the heat exchanger. Could be cause it's smaller.

The issue is all that trash in picture at end of heat exchanger where the flow reverses. This a jelly/ malt o meal consistency around where zinc resides.

Trash is not in system, cooler before this will catch impeller pieces.

Problem has occurred in multiple Marina's, and could be from other boats. I am making a galvonic isolator for the boat that is movable to each recepticle.

Any ideas?

If you are finding the heat exchanger anode almost gone regularly then you need to change it more often. Usually it is recommended to change it when the anode is half gone.

The big plate zincs on the transom CANNOT protect the heat exchanger.
That's why the pencil zinc is placed in the heat exchanger.

You must check them, the heat exchanger zinc, frequently enough to determine how long they last and adjust YOUR schedule to suit. You are not doing the change nearly often enough.

When they are half gone is time to change the pencil as Commodave suggests.

Start checking and changing that zinc every month. If the zinc is less than half gone change it but extend the check/change interval from a month to two months. DO the same at the 2 month interval and so on untill you find out how long the half gone point is reached.

I don't know what that mess is although it almost looks gelatinous. Is it?

Upon 2nd look the heat exchanger looks like it has a mussel growing in the upper R.H. quadrant. Time for a proper cleaning and also for you to go through the rest of the system, gear cooler, sea strainer, sea cock and so on.
Once those things start they can fully block the seawater or so badly restrict the raw water flow that the engine can overheat.

“The big plate zincs on the transom CANNOT protect the heat exchanger.”

I was told by American Diesel to be sure that the heat exchanger was grounded to the block / bonding system on my 135. I was wondering if that would eliminate the need for a zinc. Obviously will keep a new zinc in the Heat Exchanger but wondered what the effect would be. Boat is new to us and on the hard so haven’t had a chance to monitor results or changes.

It is gelatinous.

Coolers are clean, in fresh water for now, I barnicle buster regularly.

To get to half pencil zinc takes about three months.

Same gelatin is sometimes found on stern plates at half life.

Cigatoo said:

“The big plate zincs on the transom CANNOT protect the heat exchanger.”

I was told by American Diesel to be sure that the heat exchanger was grounded to the block / bonding system on my 135. I was wondering if that would eliminate the need for a zinc. Obviously will keep a new zinc in the Heat Exchanger but wondered what the effect would be. Boat is new to us and on the hard so haven’t had a chance to monitor results or changes.

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No. The zinc pencil *inside* the heat exchanger is the sacrificial part of the electrical circuit of metals within the heat exchanger only. What you do to the outside of the heat exchanger doesn't change that.


Ken

Choices said:

It is gelatinous.

Coolers are clean, in fresh water for now, I barnicle buster regularly.

To get to half pencil zinc takes about three months.

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Three months is not an unusual amount of time at all.


Ken

Barnacle buster probably will dissolve zinc.

bayview said:

Barnacle buster probably will dissolve zinc.

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Could be. BB is a mix of HCL acid and phosphoric acid. I would worry more about the non- replaceable metals, notably any aluminum in the coolant path, if any. Old school motors may not have any Al.

diver dave said:

Could be. BB is a mix of HCL acid and phosphoric acid. I would worry more about the non- replaceable metals, notably any aluminum in the coolant path, if any. Old school motors may not have any Al.

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The instructions say to remove Magnesium or Zinc anodes before using.

I don't use that much, but......

May get an old zinc and experiment.

Really wondering what the gell is.

Choices said:

It is gelatinous.

Coolers are clean, in fresh water for now, I barnicle buster regularly.

To get to half pencil zinc takes about three months.

Same gelatin is sometimes found on stern plates at half life.

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1) do not run BB through with zincs in unless you plan to change zincs immediately after

2) sounds like you need to be changing that zinc every 3 months

I was having to change zincs often (i.e. every 3 months) until I put a galvinic isolator in, not it looks like I can get 6 months. There are so many variables, one is neighboring boats which you cannot control

Even if a zinc appears 50% it may actually be 0%. Reason being because some zincs are made with other materials, metals, and the zinc gets eaten out first, leaving some other stuff that isn't zinc. Find out if your anodes are 100% or comprised of other metals.

As for the gel, that does not look good. When is the last time you had your entire cooling system cleaned/serviced/replaced? Barnacle buster is not a magical solution that lets you get away with skipping major service intervals...

Looks like BB was used and not thoroughly flushed out. Some residue remained and zinc sat in it.

Ok, first we need to get the terms correct. You say the boat is in fresh water and you are using zinc as an anode. If the boat is indeed in fresh water your anode should be either aluminum or magnesium, not zinc. If you are using zinc as a generic term for the anode, that is confusing. I much prefer using the term anode since that covers whatever you are using. So is the boat in fresh water and are you truely using zinc as the anode? If so then you should change to either aluminum or magnesium. If the anode is wasting to 50% in 3 months, then your schedule should be 3 months for replacing the anode. I have used BB with the anode in and it did loose some of the anode, but I was going to replace the anode immediately after the BB.

As to what the crud in the heat exchanger is, who knows. I would clean it out and run the boat for a while and then check and see if it comes back. If it does then I would spend more time trying to figure it out. If it does not return then you are good.

My bad.

Aluminum anodes except stern which has one each aluminum and zinc.

Not from barnicle buster or old coolant, all just changed in annual maintenance. Been 20 long hours since I used it. Engine is perfect.

I have found this every time I clean cooler and change that anode. May shoot message to Steve....

Choices said:

My bad.

Aluminum anodes except stern which has one each aluminum and zinc.

Not from barnicle buster or old coolant, all just changed in annual maintenance. Been 20 long hours since I used it. Engine is perfect.

I have found this every time I clean cooler and change that anode. May shoot message to Steve....

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you dont want to mix and match anode types. pick the right type for your waters.

Yes, you need to stick to one type of anode based on the waters you have the boat in. The hull anodes can be one type and the heat exchanger can be a different type because they are considered seperate bodies of water. But all the hull, shaft, rudder anodes should be the same type.

kchace said:

Three months is not an unusual amount of time at all.


Ken

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On my 135’s I change the heat exchanger anodes at 3 months. One month longer they are completely gone.

Found that gel in my Onan heat exchanger. Nobody I talked to had any idea. It seemed soluble in water, so I changed the aluminum anode and everything seems fine. I haven't used any kind of cleaner in several years, so I was figuring it was the residue from brackish water and the aluminum anode.

Ted

Well at least someone else has seen it.

We are in and out of fresh and salt water. It is common to run both plate compensations.

Cigatoo said:

“The big plate zincs on the transom CANNOT protect the heat exchanger.”

I was told by American Diesel to be sure that the heat exchanger was grounded to the block / bonding system on my 135. I was wondering if that would eliminate the need for a zinc. Obviously will keep a new zinc in the Heat Exchanger but wondered what the effect would be. Boat is new to us and on the hard so haven’t had a chance to monitor results or changes.

Click to expand...

Cigatoo,

No, it will not eliminate the need for the pencil zinc/electrode in the heat exchanger. The ground through the engine block won't hurt but it cannot replace the dedicated pencil zinc. Same for any other interior item such as seastrainers, gear oil coolers. SOme gear oil coolers may not have a zinc but the better ones do. Be cautious with the zincless units as they fail much more frequently than those with a zinc unless of course the zinc is not changed enough.

Once the boat goes back in the water check that zinc as I described untill you KNOW what the interval is.

Just another note is when checking that eroded zinc use a small wire brush to abrade away loose stuff. There will be some and it can look like there is a lot more electrode remaining than there really is.

Choices said:

Well at least someone else has seen it.

We are in and out of fresh and salt water. It is common to run both plate compensations.

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Bad idea

Use aluminum then

Plus 1 on using aluminum. It is good for both fresh and salt water. I would absolutely not mix the anode type on the hull. Just because someone else does it doesn’t make it right.