HELP! Mercruiser riser exhaust gasket surface won't clean without damaging surface!
 

Doing some maintenance on my boat which required to pull off the exhaust risers.

Its a carbed Mercruiser 465hp 502

The exhaust riser gaskets seemed to have an antisieze gray type coating on them, and they came off easily with no issues.

The issue now is that I'm trying to clean the gasket surfaces and nothing is working. It seems as though the gasket surface was powdercoated which I have never seen before. I can't get aggressive with stripping the gasket material because the aluminum is soft and I don't want to damage it.

Any info on whats going on here or what I should do?

http://i.imgur.com/5U7wb1F.jpg

wire brush and kerosene...

wire brush in cordless drill, be sure and stuff the ports first.[ATTACH=CONFIG]526344[/ATTACH]

CArb cleaner and sharp razors. Take's a bit but you won't reove any aluminum.

Just scrape, brush or grind it back to bare aluminum, then a light bead of copper rtv with a new gasket.

Of course you can always go the overkill route, chuck it up in a mill and hit it with a flycutter. Thats going to extremes, but then again, who around here goes to extremes??

Got it all done, I blocked it and got it perfect.

The coating was so thick and tough all the wire brushes and wheels were doing was marring the aluminum. All is good now!