Removing old corrosion from threads on bearing carrier retainer (Merc III)

[donwhiteside]

Hi- I picked up a used Mercruiser III unit "just in case" as a spare for the one on my 1973 Cruise-a-Home. The unit is sitting in my driveway, appears in good shape (no corrosion on cases, turns free and easy, reportedly from a boat that burned and has been sitting dry for 20 years).

It was missing the bearing carrier retainer (gear housing cover), which I found and bought. This is a large threaded ring that surrounds the prop shaft. The threads on the aluminum case are caked and filled with what looks like dirt, gunk, and probably corrosion. This prevents threading the retainer all the way in.

I'd appreciate suggestions on how to remove this corrosion, without damaging the threads. I've scraped some, but don't want to gouge anything. Is there a chemical, or other solution?

thanks,

Don

 

[Bondo]

Re: Removing old corrosion from threads on bearing carrier retainer (Merc III)

"Mercruiser III"

Though I may have Heard of 1 of these,........ I can't remember ever Seeing 1.......

If I were starring at Your dilemma,......

I'd have that old casting right up on the Bench,.. With some Good Lighting,+ My Glasses on,.....
So you can See,....
Your about to perform Brain Surgery.....

Even with some sort of Magic Potion,..... It's going to take Alot of Scrapping,+ Digging to restore those Threads......
I'd start by looking for a "Thread File" that had the Thread Count that you need,......The 1s I have would need the end ground down abit to Work,... As you'll be Bottoming the Threads,+ My Files aren't cut All the way to it's End........
Then find a nice Quality set of Picks,....... Nice Handles,+ maybe a couple of different bend Angles.......

Then take the Time,+ Have At It.......

 

[donwhiteside]

Re: Removing old corrosion from threads on bearing carrier retainer (Merc III)

Thanks, solved it. Scraped and picked (dental tool) as aggressively as I could without getting into the metal. Then smeared a bit of valve grinding compound on the huge "nut" that screws in, and slowly worked it in, backed it off, cleaned, repeat, etc. etc. etc. Eventually it all cleaned up, smooth and easy and appropriately tight.

Don

 

[Bondo]

Re: Removing old corrosion from threads on bearing carrier retainer (Merc III)

Ayuh,.........

I like Your Idea Better than Mine,................