Late 70's early 80's Merc 7.5hp cover gear housing tool

[gopdahl]

Hi all,
I have an older (late 1970s early 80's) mercury 7.5 hp 2 stroke and I'm desperately trying to remove the prop shaft cover gear housing nut but it requires a special tool. I've tried making tools but they've all broken. I also see that it is a left hand thread nut. Does anyone know the part number for the tool I would need to remove this and where I can find one? All the tools I've found appear to be for larger units.
Thanks

 

[racerone]

I have one that is home made.------Piece of pipe with 4 keys welded on.

 

[gopdahl]

Yeah, my last one was a 2" holdsaw with the non-key parts cut out. It seemed to be working well until the key parts sheared right off. It's very tight.