electrolysis questions

[AntsGrady]

Hi All,

I have a 96 50hp johnson and i'm having electrolysis issues. The small zincs that come on the unit don't seem to be doing much. I'm looking to add but don't these zincs need to be in the water to prevent the damage? I ask because the factory ones don't which i don't understand.

thanks,
Anthony

 

[Vic.S]

Hi All,

I have a 96 50hp johnson and i'm having electrolysis issues. The small zincs that come on the unit don't seem to be doing much. I'm looking to add but don't these zincs need to be in the water to prevent the damage? I ask because the factory ones don't which i don't understand.

thanks,
Anthony

Yes they are only effective when in the water, but which anodes are you looking at. The ones on the transom brackets? Presumably been found to be advantageous

possibly more important is the one in the gearcase just above the antiventillation plate and the one on the propshaft bearing housing,

(Some motors have one in the cooling system in the powerhead too)

What "electrolysis" issues are you having?

Model number ??

 

[AntsGrady]

Thanks for replying. Whats happening is my hydraulic is actually being eaten away. The drain screw for my trim fluid actually had to bre replaced because of it. This motor doesn't have a spot for a zinc above the intakes so i put a " U " anode on where the lower unit connects to the motor but don't think that is helping. I don't have any for the transom brackets and not sure there is one made to fit. I've only seen the little zinc which is connected to the side of the transom but on the inside by the hydrolics. As you suggest maybe i need to look harder for something that can bolt to the bottom of the transom. Something similar to my 225.

 

[tblshur]

is your ground wire from the enjine block to the exhaust or (midsection), connected may check that and all ground connections may help. is the motor on an alum boat?:joyous:

 

[Vic.S]

Thanks for replying. Whats happening is my hydraulic is actually being eaten away. The drain screw for my trim fluid actually had to bre replaced because of it. This motor doesn't have a spot for a zinc above the intakes so i put a " U " anode on where the lower unit connects to the motor but don't think that is helping. I don't have any for the transom brackets and not sure there is one made to fit. I've only seen the little zinc which is connected to the side of the transom but on the inside by the hydrolics. As you suggest maybe i need to look harder for something that can bolt to the bottom of the transom. Something similar to my 225.

OK then. You have a model with power tilt or tilt and trim.

I think tbishur may be thinking along the right lines.. An electrical problem rather than any deficiency of the anodes.

There are a number of variations listed so get the model number and go to the relevant diagrams on the BRP, or other, parts website and check that all grounding cables are in place and making good connections.
Also check the general state of the electrics,looking for shorts to ground and bad connections especially of negatives and grounds.

If you leave the boat with a power supply hooked up while in dock, for battery charging perhaps, this could be causing problems if not fitted with a galvanic isolator or zinc saver

 

[AntsGrady]

thanks for the replies. The boat is fiberglass and the ground to the midsection of the engine did have to be repaired as the wire broke. I'm not too sure if more electrolysis occurred after this. There is only the motor and the bilge connected to the battery so not to much to look at there. I'll have to test any other grounds. The transom has a metal plate for supporting the motor and I'm wondering if this is contributing to it. Not sure if I'll ever find all the issues and my thinking is the zincs are my best bet. It just doesn't look like there are to many places to put them so they are in the water. I will have to look again if i can put a zinc bar at the bottom of the transom but if i recall its not a fit.

 

[Vic.S]

thanks for the replies. The boat is fiberglass and the ground to the midsection of the engine did have to be repaired as the wire broke. I'm not too sure if more electrolysis occurred after this. There is only the motor and the bilge connected to the battery so not to much to look at there. I'll have to test any other grounds. The transom has a metal plate for supporting the motor and I'm wondering if this is contributing to it. Not sure if I'll ever find all the issues and my thinking is the zincs are my best bet. It just doesn't look like there are to many places to put them so they are in the water. I will have to look again if i can put a zinc bar at the bottom of the transom but if i recall its not a fit.

Making sure there are no electrical defects that may cause electrolysis should be the highest priority I think as the zinc anodes won't offer any protection against that. Its effects can be severe and quick!
The zincs will only protect against what is called "galvanic corrosion" which is what can occur when two dissimilar metals, connected to each other, are immersed in seawater.

What metal is the plate supporting the engine? If it is in contact with the water then it could be contributing to the corrosion. Perhaps not if it is aluminum but very definitely if it is stainless steel More zinc anodes on the affected parts will then be the answer.

Make sure any zinc anodes you buy are made of an alloy that complies with the US military specification A-18001-K.( which importantly has a very low iron content)

 

[AntsGrady]

Thanks Vic. I believe the plate is stainless. I see no pitting on it however but did think this could be an issue after my reading. Problem is finding places to put more zincs that will stay in the water.

 

[AntsGrady]

Oh and the model is johnson 50 TLEDS 1996

 

[AntsGrady]

Wondering if a transom mount zinc is the answer. Newver did this but maybe drill a couple holes through the transom below the water line, fill with sealant and bolt the zinc on. Then do I need to run a lead to the motor?

 

[steelespike]

I assume you are in salt or brackish water.
You need to be sure all the metal is bonded together Like your trim assembly if it and the motor aren't bonded together with a wire or metal strap
or by the contact of all the components Any metal that is isolated from any number of metal components of various parts of your boat.
There could be stray voltage in the marina or a neighboring boat.Any ground from the electrical system needs to be hard wired back to the battery
or the motor drivetrain assembly. Not to an aluminum hull.If your trim plug is screwed into a plastic component or if there are 2 different metals in contact
they can react.If your in fresh water suspect stray electric.in the boat wiring or the neighbor or marina.

 

[Vic.S]

Thanks Vic. I believe the plate is stainless. I see no pitting on it however but did think this could be an issue after my reading. Problem is finding places to put more zincs that will stay in the water.

I assume the stern brackets are simply clamped or bolted to the stainless plate with no electrical insulation between them. If so and it and the brackets are wetted by seawater the brackets may well suffer from galvanic corrosion.. Additional anodes on the brackets may help to reduce this.

Oh and the model is johnson 50 TLEDS 1996

Thanks for posting that. Forget about most of what I said about anodes on the lower unit, Just one on the propshaft bearing housing behind the prop AFAICS

Wondering if a transom mount zinc is the answer. Newver did this but maybe drill a couple holes through the transom below the water line, fill with sealant and bolt the zinc on. Then do I need to run a lead to the motor?

The zinc anodes need to go on what they are intended to protect or be bonded electrically to it. They will corrode away fairly quickly if fitted to the stainless steel plate or too close to it but they won't be doing anything useful by way of protecting the motor mounts. They need to be on or close to the mounting brackets.


Maybe by repairing the broken ground wire you have done all that is really necessary..


Generally problems in marinas are caused by connection to the shore electricity supply......... It leads to all the boats and the marina steel work all being connected together by the ground connections. Galvanic isolators (aka zinc savers) are usually the solution to this.

 

[AntsGrady]

Thanks Vic and all.

 

[AntsGrady]

No Title

So hear are some picks of the transom. The problem is the lower left corner here. You can also see the metal plate on the transom. It was also suggested to me to remove the bottom paint an inch around the plate. Also attached is the zinc i've made. I was going to attache one end to one of the holes at the bottom of the transom and put the zinc in my bilge as it always has water and should complete the circuit and draw the electrolysis. Any thoughts?

 

[Vic.S]

put the anode on the outside of the transom, low down so that its in the water as much as possiible, at least when at rest.and run a bonding wire to the motor. Directly to the parts you need to protect if possible

No good fitting it in the bilge I dont think. Not if you are trying to protect parts on the outside

That anode is made from the correct Mil spec zinc I hope.

 

[AntsGrady]

thanks Vic. it is the correct zinc. its not easy mounting additional zincs here so i'm a bit limited. I had a tip that the cable will pass the electrolysis to the zinc as long as it sits in water no matter where that is and worked for someone else. guess we'll see. the other thought was to get a bolt in motor transoms right side hole and get a zinc on the other side. I'd have to clean all the paint off at this point. I'd like to put it on the left side but the hole is not fully accessible as the trim sticks out a bit.

 

[Vic.S]

The anode has to be in the same body of water that is corroding your hydraulic system. Not in separate puddle somewhere.

The rule of thumb for fitting anodes is that they must be "able to see" the part(s) they are fitted to protect .

 

[AntsGrady]

Yeah I am not completely convinced this method would work but it's coming from a reliable/educated source. I am going to continue to see if I can get a better option. I still can't get over the factory zincs and where they are installed. They never hit the water.