Saving Old Seagulls

I have been stripping down my forty plus to tidy it up and the bracket that holds engine onto transom mount had seized screws, I used heat and screws started to give then sheared off Now I have a spare but it has a plastic clamp, it looks like it fits, any issues with this one and I need to replace screws, could anyone tell me which size of screws are required?

5/16 BSF

Hi,

It is used studs and nuts there instead of screws. Those studs have holes in the end for the locking pin or wire to avoid the nuts coming undone and the engine fall.
Screws doesn't have a way to be locked so be careful. On this part of equipment the studs stuck badly because of the corrosion. Heat of course can solve the problem, I mean about 600-800C, not gentle things

The thread size is BSF 5/16" 22TPI.

Only heat aluminium for this purpose to a temperature where spit will bounce off it, higher than this will anneal it & the majority of casting alloys of aluminium melt between 550 & 650 degrees C.

Thank you gents

Be careful with heating thin alloy, it does not change colour with heat until it goes a little shiny then it's too late, followed by a little puddle been there several times