Corrosion/Electrolysis Damage to Engine Lowe Unit

[turnto55]

Hello Ranger tug people. I am Cliff Palmer, father of Mike Palmer who purchased a R-23 in June 2018. We like the boat and keep it in Baltimore harbor. We previously were sailors. Upon pulling the boat for winter storage in early Dec. 2019, the marina found extensive corrosion/electrolysis damage in the front part of the lower unit. That portion of the motor has always stayed slightly [3" to 4 "] in the water even when the engine is in the fully tilted up mode. Has anyone else ever experienced this? It would seem the engine is mounted too low or it is not tilting up as much as it should. We are looking at a several thousand dollar repair/replacement of the lower unit. However, before proceeding we want to know what the long term correction is to this problem. I recently[several days ago] sent an e-mail with photos of the lower unit to customer service at Ranger Tugs, as well as the Md. dealer we purchased the boat from and am waiting to hear from them. Would appreciate hearing back any useful info. or experiences. Cliff Palmer

 

[knotflying]

Not all outboards when lifted come completely out of the water. Electrolysis is a common issue with every boat, especially in a marina environment. Placing a sacrificial zinc that is connected to the battery negative and/or a galvanic isolator is the best precaution.

 

[Gwbru]

Turnto55, I had the same experience with my 2019 R23 Yamaha, although at this point it doesn’t sound as critical. When I pulled the boat in November, the yard noticed the beginnings of damage. Hopefully, we caught it early enough. I know I’m guilty of leaving the shore power plugged in and battery charger on more than I should, but the cold beverages in the fridge are an important part of my summer enjoyment.
A couple points I am considering (besides limiting shore power and battery charger overuse) is to add a Galvanic Isolator and whether it would make more sense to leave the engine more submerged to allow the zinc that is above the prop to work.
Any other thoughts or guidance would be appreciated.
Greg

 

[TugScout]

I'm a huge proponent of galvanic isolators. I keep my boat in the saltwater in a covered slip with the shore power connected 24/7. In the past I was replacing zincs every six months and they were noticeably deteriorated when removed. After installing the isolator, I can go 12 months and upon inspecting the zincs, they almost look like new.

I've installed the ProSafe 30 on both my current R-27 Classic and my previous R-21EC with excellent results.

https://www.amazon.com/ProMariner-22034 ... 206&sr=8-1

Cheers,

Mark

 

[gsc3]

I had same problem with Yamaha 300HP and CW-24. Below is a copy of my post from Jul 27 2017:

"Galvanic corrosion is a hazard for boats that are docked near steel seawalls or concrete seawalls reinforced by iron rebar and are connected to shore power. The problem is particularly bad for boats with underwater aluminum fixtures, such as outboard lower units. Unplugging the boat’s power cable from the dockside AC outlet should prevent the galvanic current that causes the corrosion. Alternatively, installing a galvanic isolator, which costs about $185, will stop the galvanic current, and the resulting corrosion, even with the boat connected to shore power."

Since installing the galvanic isolator in 2017 there has been no corrosion effect on zincs or lower unit. However, I also added 400 pounds of lead to the chain locker to lower the bow and lift the stern, so the lower unit out of the water in its "up" position, unless the fuel tank is more than half full, in which case about 1-2 inches of lower unit is immersed.

Slade Cargill, Sojourner, CW-24, Longboat Key, FL

 

[Andrew Custis]

This should help you in regards to zincs and how to maintain your underwater metals. I copied and pasted this from what I had sent to all of our dealerships around the country. Hopefully, this information has been shared and it can provide some insight on the best route to protect your underwater metals.

The first thing you will want to determine is if the owner plans to leave the boat on a trailer or in the water. If the owner says that they plan to keep their boat in the water, you need to make sure you are determining the best steps to make sure they are protected.
1. Will you be leaving the boat in a slip full time?
2. Will you be keeping it on a lift where the boat will come out of the water each and every time?
3. Will you be keeping it on a mooring ball?
4. Will you be plugging the boat into power?
5. Will you be plugging it into power at your house or at a marina?

Each one of these questions should lead to a different response on how they will need to take care of their boats.

1. Perfect. These boats are built to leave in the water but we need to take some extra precautions to make sure you are best protected. First, we need to determine what kind of bottom paint we are going to apply. Second, we need to make sure the trim tabs have zincs on them and third, we need to make sure the zincs installed are the appropriate type for the water you will be keeping the boat in.
2. Great! Keeping it on a lift is like keeping it on a trailer. You want to make sure the boat will fully come out of the water as we will not be taking the same precautions as if your boat was sitting in the water. If it stays on the lift, do you plan to cruise for more than 90 days at a time? If so, we should still look at doing bottom paint. We should also look at adding zincs to the trim tabs to make sure all of your underwater metals are protected.
3. Not a problem. This is just like keeping it in the water. We will need to take the same steps as if we keeping it in a slip as stated in item number 1.
4. This can make significant changes to your boats systems and underwater metal protection. All boats today are built with the highest electrical shock standards which now include an ELCI breaker which now monitors the grounding of the entire boats grounding system. In addition to this, ABYC and NMMA require the manufacturers to bond their 12 volt grounding to their 120 volt grounding to prevent electrical shock to the water. Because this is done, this can make your boat susceptible to sharing grounding with your neighbors on the dock which will cause your zincs to deteriorate much more rapidly versus if you left the boat unplugged.
a. How should we make sure that I am protected? The easiest way is to put your boat in the water and inspect the zincs deterioration on all underwater metals to see how long they are lasting. I suggest doing this at the 30 day mark and at the latest, 90 days. If they are corroding too quickly, we need to look at installing a galvanic isolator which will isolate your grounding from your neighbors who are using your zincs and potentially adding more zinc to the boat such as a grouper zinc you hang in the water or a permanently mounted zinc that we can install on the transom. After this is done, you will then need to monitor the zincs at the next 90 days to make sure that we have it under control.
5. This doesn’t always change things but the same steps need to be taken as number 4.

We have measured two different boats a year apart and here are the readings that were obtained. Keep in mind, protected boats should be from -950MV to – 1100MV for a fiberglass boat with aluminum outdrives.

1. Hull Number 2356-2019
a. This boat is brand new with new zincs.
b. NOT PLUGGED INTO POWER. ZINCS are at 80% remaining.
i. @ Engine block = -1008 MV.
ii. @ Thru hulls = -1011 MV
iii. The boat is well protected and within the suggested range. Zincs still need to be monitored as described in section 4A to determine the life of the anodes.
c. PLUGGED INTO POWER
i. @ Engine block = -850 MV
ii. @ Thru hulls = -852 MV
iii. The difference in MV shows that this is a hot marina and by plugging in we are seeing changes that will cause the zincs to deteriorate more rapidly. The customer will need to install a galvanic isolator if they are leaving the boat plugged in full time. Follow the zinc inspection period and determine the life you can get out of the anodes.
2. Hull Number 2363-2018
a. Boat is one year old and zincs are at 20%. Zincs have been changed on this vessel three times in the course of a year. Customer was monitoring per the engine owners manual and took precautions to extend the life of the zincs by installing a transom zinc and a galvanic isolator.
b. NOT PLUGGED INTO POWER. Zincs are at 20% remaining.
i. @ Engine block = -980MV
ii. @ Transom zinc bonding = -1006MV
iii. @ Thru hulls = -1043MV
c. PLUGGED INTO POWER
i. @ Engine block = -980MV
ii. @ Transom Zinc = - 1004MV
iii. @ Thru hull = -1008MV
iv. All of these numbers indicate the boat is protected and the difference between being plugged in and not plugged in show that the Galvanic Isolator is doing its job.

 

[Kimberly Dawn]

Great post, Andrew. Thanks!

 

[Chimo]

Excellent information! Thanks Andrew. We added a GI a couple of years ago as we were changing zincs every 3 months. We now change every 6 months when we do a scheduled haul out. Could probably go longer but as we wouldn't reach annual intervals there's no reason to extend.

Question: You say you are measuring potential, for example at thru-hull fitting or engine. What's the reference point; i.e. between engine and which point?

Thanks

 

[BB marine]

That is a very good information and explanation of the value of the galvanic isolator. I believe this is a must for boats that stay in the water and connected to shore power. Adding additional anodes will help too. When a Yamaha is trimmed up while in the water one of the anodes becomes in active reducing the amount of protection. The trim tab anode if used or the flat anode plate if installed in place of the trim tab is out of the water.The next statement to be careful saying is zinc instead of anode. I believe the original installed anode from Yamaha is Aluminum alloy. An aluminum alloy anode will give better service life in salt water then a zinc anode. Most outboard manufacturers Recommend only Aluminum alloy anodes used with their aluminum gear housings in salt water. ABYC also recommends aluminum alloy anodes for all applications in polluted fresh water, brackish and saltwater and claim longer life expectancy of the Aluminum alloy compared to Zinc. The aluminum is slightly more active then zinc but has proven to give more protection. Mercury marine posted a service bulletin back in the 90’s about the use of aluminum instead of zinc. Mixing anodes will add even more issues so make sure all anodes are the same material. It has been a term used for years. “ I need to change my zincs” You need to change your anodes with the appropriate material.If you have a stern drive or outboard used in brackish or saltwater the choice should be aluminum. Magnesium if in clean fresh water.

 

[Red Raven]

Excellent information! Thanks Andrew. We added a GI a couple of years ago as we were changing zincs every 3 months. We now change every 6 months when we do a scheduled haul out. Could probably go longer but as we wouldn't reach annual intervals there's no reason to extend.

Question: You say you are measuring potential, for example at thru-hull fitting or engine. What's the reference point; i.e. between engine and which point?

Thanks

Hi Chimo,

The measurement Andrew is talking about is between the stated locations and the water the boat is sitting in. You need to use a silver/silver-chloride reference electrode that drops into the water like this:

https://www.boatzincs.com/corrosion-reference-electrode-specs.html

Silver/silver-chloride is used because it adds minimal error due to its very small galvanic potential.

Curt

 

[Chimo]

Thanks Curt, as always a great answer.

 

[Don55]

How effective are galvanic isolators? I have a R23 I bought a year ago last February. The boat is in the water on my dock behind my house. I live in Florida. At the first engine service the boat was hauled and electrolysis damage was discovered. I had a galvanic isolator installed and the damage repaired. Just had the boat hauled for the annual service and found severe corrosion on my lower unit so severe that they recommend replacing the lower unit. This is not cheap. My engine in the full up position still leaves the forward portion of the lower unit a few inches in the water. Question, why didn’t the galvanic isolator protect my boat and how can I keep this from reoccurring?

 

[ohioan55]

I would like to add that not all zincs work well in all types of water. While a zinc anode works best in salt water, as you travel into brackish water, they lose their effectiveness and you may be better served with an aluminum anode that will work in both salt and brackish water (the outboard mentioned earlier was the aluminum anode and the water in Baltimore is not the saltiest). If you stick mainly to fresh water, use magnesium anodes as these are best suited for a 'less active' environment. Andrew's post is good, but the moral of my advice is 'know your water and pick your anode accordingly'. I ran into a similar issue to the one mentioned at the start of this thread. About 15 years ago I purchased a Beneteau with an 8 hp Honda. The boat had been kept near Annapolis, MD in the water for much of the year. The boat stayed connected to shore power most of the time. The outboard was connected to boat electrical system so that it could charge batteries while running. I has tested the motor and it ran great, I just didn't test it in water where it had to pump it's own water. After find that it didn't pump, disassembly revealed that the interior of the lower unit had been eaten up with stray current corrosion. It only attached the aluminum parts. So with this said, and in the Chesapeake Bay in particular, salinity changes the further north you go with it ending up being freshwater at the mouth of the Susquehanna. My advise in the bay, use aluminum 'zincs' and a galvanic isolator.

 

[Red Raven]

How effective are galvanic isolators? I have a R23 I bought a year ago last February. The boat is in the water on my dock behind my house. I live in Florida. At the first engine service the boat was hauled and electrolysis damage was discovered. I had a galvanic isolator installed and the damage repaired. Just had the boat hauled for the annual service and found severe corrosion on my lower unit so severe that they recommend replacing the lower unit. This is not cheap. My engine in the full up position still leaves the forward portion of the lower unit a few inches in the water. Question, why didn’t the galvanic isolator protect my boat and how can I keep this from reoccurring?

Don55,

A galvanic isolator is only effective against galvanic voltages and currents coming through your shore power connection. It does not protect against other sources of corrosion including; galvanic potentials on the boat, other electrical potentials on the boat, or voltages on the shore power grounding wire above galvanic potentials (above 1.2 volts).

Galvanic potentials on the boat: This is what your anodes protect against. An Isolator does not help this. What shape were the anodes in when you found the damage to the lower unit? If they are working properly the anodes should corrode before there is damage. If they are missing and fully corroded away, are insulated by oxidation, or not bonded to the lower unit they cannot protect it. A multimeter can be used to test for proper bonding, oxidation on your anodes should be cleaned off, and anodes should be checked and replaced regularly. The proper level of anode protection can be tested using the reference electrode described in the earlier post to this thread. As Ohioan55 says you made need different anodes.

Other electrical protentials on the boat: if you have battery voltage exposed in salty bilge water can create a lot of current and do damage very quickly. Check for any exposed wires in the bilge. Check for voltages above 1 volt on your bonding system.

Other shore power voltages: a fault in the shore power system could be creating voltages on the grounding wire above galvanic potential (and thus above the isolators 1.2 volt limit for protection). Check the potential on the grounding wire using the reference electrode discussed above. Test your galvanic isolator per the included instructions. If all else checks out disconnect your boat from the shore power by fully removing the plug when the batteries are charged.

Hope this helps.

Curt

 

[BB marine]

Question, why didn’t the galvanic isolator protect my boat and how can I keep this from reoccurring?

The Galvanic isolator does not protect your boat from galvanic corrosion it helps isolate your boat from other boats so the protective anodes mounted on your motor and boat are just protecting your boat instead of other boats in the marina. That is a basic description. If your boat is docked behind your house and there are no other boats that are plugged into the electric service that your boat is plugged into the isolator isn't doing much for you. Do you have a steel sea wall? Have you tested the water around the boat and dock behind your house. Have you checked the electrical supply at the dock and the ground?

What is the condition of your anodes? How often are they checked. The anode protecting the lower unit is out of the water if you have the motor raised up. There is also an anode attached the the transom plate. What other anode protection do you have on the boat? With the trim tab anode out of the water the only way for the transom plate anode will protect the lower unit is if there is continuity from the transom plate to the lower unit. If there isn't the lower unit is not protected. What material anode are you using? I would advise aluminum alloy anode over Zinc. It will protect the lower unit better. In area's that have higher activity anode inspection should be done more often along with replacement. In areas that have higher activity additional anodes may be required. If it is your personal dock behind your house you need to find out why the activity is so high. You need tp protect your boat accordingly. Have an ABYC certified electrician inspect and check your dock power supply and your boat. He /she will be able to determine what needs to be done to help with the issue.

 

[Don55]

Found the answer to my galvanic isolator question. They don’t work if they are not connected. The electrician just finished connecting my isolator correctly and everything checks good. I am sending the repair bill to the dealer as this seems a clear case of negligence.

 

[jrnunezmd1]

How I can know if my boat, a C24- Coupe have a Galvanic Isolator?

 

[Cutwater28GG]

Don55,

A galvanic isolator is only effective against galvanic voltages and currents coming through your shore power connection. It does not protect against other sources of corrosion including; galvanic potentials on the boat, other electrical potentials on the boat, or voltages on the shore power grounding wire above galvanic potentials (above 1.2 volts).

this is super important to understand. you can have a neighbor boat pouring electricity into the water that your galvanic isolator can do nothing about. IMHO this is a far bigger cause of excessive corrosion than your own boat. you just have to keep up on zinc replacements

I'm curious did the original poster change their zincs between June 2018 and Dec 2019? because any boat in a marina for 18 months with no zinc changes will have used up the zincs long ago. resulting in corrosion elsewhere