93 60HP - seized bottom pin for trim motor assembly

[twr7cx]

I have a 1993 Mercury 60HP 3 cylinder 2 stroke twin-carb motor - it has the single cylinder hydrualic trim with an electric motor. The trim motor has recently started playing up, so I have pulled it apart and given the electrics a freshen up - seems to be working much better now.
But I have a related issue. The bottom pin that holds the trim motor to the frame assembly (these arn't the proper terms I'm sure - I'll try to get photos tomorrow to help explain what I'm talking about) seems to be seized in place. It is on this bottom pin that the trim assembly is ment to rock as the motor goes up and down, but since it is seized in place the trim motor seems to rather be flexing and bending and I believe this is causing the issue I'm having with the motor not operating smoothly.
In an effort to remove this bottom pin, I have removed the dowel, use plenty of penetrating spray and whacked it so hard that I have started to flatten out the top of my 12mm pin punch (and it's not a cheap brand one either!).
Any ideas on how I could remove it? I'm running out of ideas here, and I'm not sure I could take it to somewhere with a press as it might damage the frame.

 

[twr7cx]

Re: 93 60HP - seized bottom pin for trim motor assembly

I think that Caustic Soda (usually available from hardware or pharmacy {a weak alternative is washing soda available from supermarket}) will dissolve Aluminium Oxide, and then I can use Nitric acid to remove the smut (residual alloy material).