Mercruiser - Outdrive corrosion on transom assembl

B

bomguthrie

Member
Joined
Nov 22, 2013
RO Number
33514
Messages
9
I have some corrosion behind where the label is for the outdrive. It almost looks like there were originally two holes and that been corroded out more.

My mechanic says this is the sign of big trouble and the engine must be pulled, along with the outdrive and the assembly replaced.

He also said this could be causing some leakage in to the bilge.

Seems like I would just remove the corrosion, use some corrosion inhibitor, then seal up with 5200.

https://dl.dropboxusercontent.com/u/71616959/sundancer - stern drive.JPG

Thoughts, experiences?

Thanks, Mark

St. Petersburg FL
Searay Sundancer 280
Twin 4.3 Mercruisers I/Os
 
I'm not a boat mechanic per se. I just work on my own and I would try the fix you mentioned before I would tear it apart. After you are done paint the drive with Mercury black then antifouling paint. My boat, "88 alpha 1, is in brackish water 7 months and Florida salt water 3 months. The drive gets painted twice a year and I have no corrosion on the drive.
 
Ouch! No your transom unit is toast. Bite the bullet and get a new one. You can get them for about 2 grand on the web. Corrosion that bad cannot be stopped on aluminum, it is over. When you put in the new one, make sure you order a new continuity kit to make sure the transom unit is connected to the drive so the anodes will protect.

Last year, I had leakage at the gimbal seal, and a bad transom sender. By the time I would have paid to repair those things, it would be cheaper just to replace the whole transom unit. When you start messing with the transom unit, it is usually cheaper to replace than repair.
 
As a post script, corrosion that bad also means your gimbal pin is toast, which is where it is leaking into your bilge. To deal with that, you have to rill and tap into the transom unit. I doubt that corroded unit will be able to hold up to the tap.
 
I just went through the same thing, only I had much worse corrosion! Picked up a very nice used transom assembly on that auction site. replaced bellows bearing and shift cable, added a mercathode and galvonic isolater to insure it doesn't happen again. It's not such a bad job as long as you have the means to pull the engine.
 
looking at the pic also shows a lot of corrosion on the whole drive. did someone leave a power cord in the water?
sundancer20-20stern20drive_zpsd9b6fa9f.jpg
 
Is there only one pic? It didn't show me enuff to warrant removal. Neither did it show cause for water intrusion. More pix will give better idea what's going on.

There are grounding cables/connections throughout the whole drive and transom assembly. Do you have them?
 
Looks to me like it is corroded completely through.
 
It looks like it started from the inside. I think that you are looking at the tip of the iceberg.
 
I just had both of mine replaced. One of them was leaking in to the bilge. Once they were out the leaking one was even worse than I thought, and the other one looked just as bad.
Bite the bullet and replace it. If the leak gets bad enough it could sink the boat.
In the meantime make sure your bilge pump is working properly and keep the batteries charged up.
 
You must log in or register to reply here.
Back
Top