Crestliner aluminum corrosion

[Captain blake]

First off long time lurker first time poster. Hope I get this right. I’ve had a few glass boats ditched them for a 1993 crestliner phantom 205 4.3 I/O got it cheap for a aluminum boat in BC Canada I have noticed lately corrosion happening on the transom with pitting. Also noticed the drive corroding as well. I’ve read some threads but all seem to have conflicting info. I don’t want a show boat but want to stop the corrosion. What’s the best way to tackle this? Also what is causing this? It’s grown in the last three years I do take it in the salt.I would love to get the transom replaced with all aluminum and a off shore bracket installed but that’s just a dream so far.

 

[eterry]

I'm 8 hours by car to the gulf coast, but your pics reminds me of cars you see driven down to Texas from up north where they salt the roads heavy. I'm guessing its simply salt water corrosion. I hear its a tough nut to crack. I'm sure someone will chime in with more experience.

 

[Emerger]

First off long time lurker first time poster. Hope I get this right. I’ve had a few glass boats ditched them for a 1993 crestliner phantom 205 4.3 I/O got it cheap for a aluminum boat in BC Canada I have noticed lately corrosion happening on the transom with pitting. Also noticed the drive corroding as well. I’ve read some threads but all seem to have conflicting info. I don’t want a show boat but want to stop the corrosion. What’s the best way to tackle this? Also what is causing this? It’s grown in the last three years I do take it in the salt.View attachment 339387View attachment 339388View attachment 339389View attachment 339390I would love to get the transom replaced with all aluminum and a off shore bracket installed but that’s just a dream so far.

You have what appears to be galvonic corrosion. You can see how it's worse around the outdrive and what seems to be a rivot in the hull. It's caused by electricity passing between the two metals. Metal tends to dissolve and flake off, traveling in the direction of current flow. It's the way electroplating works.

You should first check your sacrificial anodes on the outdrive. The anode is a chunk of zinc that is bolted on someplace that works to prevent corrosion by "sacrificing" itself. It corrodes and flakes away so that other metals like the engine and the hull don't. Remove the anodes and use a wire brush to clean the area where they contact the outdrive.

Next, remove your outdrive and coat the outside of the transom with Gluvit. It will form a barrier to protect the hull. If you can't remove the outdrive, coat as much of the transom as you can.

http://marinetex.com/products/marine-tex-products/gluvit/

 

[Scott Danforth]

that is some serious corrosion

my guess:

• someone has something wired wrong in the boat
• its a salt water boat
• or someone swapped the transom wood with pressure treated.

 

[Captain blake]

Only thing is I have added a second battery through a 1-2-off switch I’ll check to make sure the batt lugs are not touching the transom wood where I have it mounted I have the second battery ground going to the block same as the stock battery. All other wiring looks stock but I’ll look again for anything odd. I looked at the anodes do look questionable. So I’ll replace those. That’s a stainless steel bolt holding the transom wood in that looks stock. There isn’t any corrosion other then the transom that I have found at least. Now how should I deal with it? Grind it all out sand/soda blast treat it some how? Repaint? And with what? I have those skills just don’t know the procedure. Thanks for your responses.

 

[ahicks]

Prior to getting into a serious DIY transom replacement/repair, I would have a couple of welder/fab guys look at it, with an eye toward replacing that entire transom. Big project for sure, but done properly it shouldn't need doing again for the life of the boat.