motor flush port screw won't open

[Wood Zeppelin]

Honda BF40 lower unit has a flush port screw near the oil screw. But I can't get it to open.

I tried a very large screwdriver, both flathead and #3 Phillips. The flat head slips due to wear and tear on the screw slot. The phillips stays in place, but still won't open the screw. Even a #3 phillips but in my driver with the "impact" setting won't open it.

Sprayed it with WD40. Though about propane torch but I'm afraid I'll burn the paint around it.

I'm afraid a screw extractor would require too deep of a drilled hole, and would hate to drill thru and put metal chips inside in cooling system.

Any other ideas??

[thataway]

I would agree being very cautious with heat..but an electric heat gun can be enough in some circumstances. (especially if used with liquid nitrogen or even CO2 for a very small area.). For loosing use PB blaster or Aero kroil penetrating oils.