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Posted: 8/16/2016 11:53:54 PM EDT
I have 2 small pin holes in the transom with the white powder corrosion in them. The drain holes in my splash well are also rusting through. I'm trying to figure out what's causing this and hopefully I can prevent this from spreading any farther.

Has anyone experienced this and have any idea what causes it?
Link Posted: 8/17/2016 1:09:24 PM EDT
[#1]
Is it in saltwater or fresh? Do you keep it in the water? Do you have a battery charger or any shore power hooked to it when it's in the slip?

Link Posted: 8/17/2016 2:43:32 PM EDT
[#2]
I use it in fresh water.

I don't keep it in the water.

I have an onboard charger, but I don't keep it plugged in all the time.
Link Posted: 8/17/2016 3:49:42 PM EDT
[#3]
Add some anodes to the transom. Do some reading on this page.
Link Posted: 8/17/2016 6:37:59 PM EDT
[#4]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Add some anodes to the transom. Do some reading on this page.
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Thank you!

What are your thoughts on stray current in boats?

I don't know a whole lot about electrical currents. I took a volt meter and put the negative lead on the negative post of the battery. I then put the positive lead on the corrosion spots and the splash well drains and I got a very small voltage. But if I put the positive lead on a spot of aluminum that did not show corrosion there was no current.
Link Posted: 8/17/2016 7:37:28 PM EDT
[#5]
Is there any pressure treated wood on your boat?  Chemicals that are used to treat the plywood can definitely be a source of electrolysis. If you google search a combination of "treated wood" and "aluminum" you will find a bunch of material regarding their incompatibility.
Link Posted: 8/17/2016 8:47:38 PM EDT
[#6]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Is there any pressure treated wood on your boat?  Chemicals that are used to treat the plywood can definitely be a source of electrolysis. If you google search a combination of "treated wood" and "aluminum" you will find a bunch of material regarding their incompatibility.
View Quote


Yes I'm pretty sure that the transom is treated plywood. That would probably explain why I'm only seeing this in the transom and no where else. Would an anode still help in this situation?
Link Posted: 8/17/2016 9:40:39 PM EDT
[#7]
Anodes won't help if the cause is the wood touching the aluminum. Anodes are only "active" when they are submerged in water. The reason I mentioned anodes is that electrolysis can happen fast in water and

outboard motors don't have enough anodes on them to protect the hull when submerged.

Outboards usually have an anode or two on the lower unit and one on the transom bracket which are too small to protect the aluminum hull which has a lot of surface area.

Adding anodes to the hull will protect it when submerged and possibly if it's saturated from rainwater.
Link Posted: 8/17/2016 9:50:12 PM EDT
[#8]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Anodes won't help if the cause is the wood touching the aluminum. Anodes are only "active" when they are submerged in water. The reason I mentioned anodes is that electrolysis can happen fast in water and

outboard motors don't have enough anodes on them to protect the hull when submerged.

Outboards usually have an anode or two on the lower unit and one on the transom bracket which are too small to protect the aluminum hull which has a lot of surface area.

Adding anodes to the hull will protect it when submerged and possibly if it's saturated from rainwater.
View Quote


I see. Yes my outboard has the 2 anodes they look just fine.

I wonder why the manufacturer or would use treated plywood the transom if this is a common occurrence?

I used to have a War Eagle and never had any problems like this.

I'm sure that it would cost a huge amount of money to replace the transom wood.

Realistically how long could the aluminum last? Will it all corrode away?
Link Posted: 8/17/2016 11:06:47 PM EDT
[#9]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Yes I'm pretty sure that the transom is treated plywood. That would probably explain why I'm only seeing this in the transom and no where else. Would an anode still help in this situation?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
Is there any pressure treated wood on your boat?  Chemicals that are used to treat the plywood can definitely be a source of electrolysis. If you google search a combination of "treated wood" and "aluminum" you will find a bunch of material regarding their incompatibility.


Yes I'm pretty sure that the transom is treated plywood. That would probably explain why I'm only seeing this in the transom and no where else. Would an anode still help in this situation?



Not all plywood is created equal and not all plywood would cause issues. I hope the manufacturer would use proper wood when originally building the boat. I don't know as I would immediately blame the wood, but it is something to be cognizant of. When I posted I was thinking more along the lines of something that had been built in afterwards or been used as a patch/reinforcement.  More spitballing at what a possible cause could be than anything else...
Link Posted: 8/18/2016 1:15:07 PM EDT
[#10]
The boat builder could have used pressure treated wood which IIRC has some copper content to the treatment. Marine grade plywood does not. Copper will react with the aluminum causing the corrosion.

I would call the factory and check with them on what kind of wood was used. You may not get a straight answer from them but worth a try.

When we rebuilt transoms, we used marine grade plywood, then coated it in fiberglass resin to seal it.
Link Posted: 8/18/2016 10:07:23 PM EDT
[#11]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
The boat builder could have used pressure treated wood which IIRC has some copper content to the treatment. Marine grade plywood does not. Copper will react with the aluminum causing the corrosion.

I would call the factory and check with them on what kind of wood was used. You may not get a straight answer from them but worth a try.

When we rebuilt transoms, we used marine grade plywood, then coated it in fiberglass resin to seal it.
View Quote


I'll give it a try. In your experience what would it cost to have this replaced the way you rebuilt them?
Link Posted: 8/19/2016 1:00:53 PM EDT
[#12]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


I'll give it a try. In your experience what would it cost to have this replaced the way you rebuilt them?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
The boat builder could have used pressure treated wood which IIRC has some copper content to the treatment. Marine grade plywood does not. Copper will react with the aluminum causing the corrosion.

I would call the factory and check with them on what kind of wood was used. You may not get a straight answer from them but worth a try.

When we rebuilt transoms, we used marine grade plywood, then coated it in fiberglass resin to seal it.


I'll give it a try. In your experience what would it cost to have this replaced the way you rebuilt them?

It really depends on how the transom was built. If it's welded, it can run a lot of $$$. Rivets, not as much, but still expensive. If it's riveted, you can expect $1,000 or more. You would really have to take it to a shop and have them look at it for a good estimate.

We did mainly pontoon boat and small semi-vee  "row boat" transom replacements which were easy in comparison to yours.
Link Posted: 8/19/2016 1:37:21 PM EDT
[#13]
Aluminum boat? Steel mounting bolts by chance?

You may be seeing bimetalic corrosion.  Google it.
Link Posted: 8/19/2016 2:47:44 PM EDT
[#14]
Here's some pics of what I'm seeing. I've contacted the manufacturer who said they are going to reach out to the dealer. We'll see what happens I'll keep you updated.







Link Posted: 8/19/2016 8:42:41 PM EDT
[#15]
Starting to see the same in mine,esp after I ran it in seawater for a week. Typically in fairly high salinity here anway


Link Posted: 8/25/2016 1:56:44 PM EDT
[#16]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Aluminum boat? Steel mounting bolts by chance?

You may be seeing bimetalic corrosion.  Google it.
View Quote


Looks like a combination of metals and possibly leaching chemicals from the wood,
I just repaired a couple spots were a previous owner of my boat used steel screws to attach the pressure treated transom he put in

That wasn't to bad,
Compared to where someone had slipped 100 someodd steel pull tabs off old beer cans under the floor in the bow, they all ate nice little pits in the aluminum
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