The question is: What is the torque value for beam bolts?. The answer is:

I have never seen a torque value for beam bolts. I always guessed that because the condition of boats vary wildy, nobody wants to be responsible for you stripping the threads on an old corroded boat.

That said, a standard practice for 1/4" bolts threading into aluminum is 5-10 ft-lbs. This is for new clean threads. Not dirty corroded threads. For a normal boat, I consider 5 ft-lbs a maximum.

FYI the 5-10 ft-lbs is from a aircraft practice. The rest of the practice says "don't thread steel bolts directly into al in a saltwater environment".

In reality, apply anti-seize for al/steel to the bolts and threads. Clean the threads every couple of years, with a tap. Just get the bolts snug and check them frequently and keep a heli-coil kit for Al/steel handy. Pep Boys sells a good SS heli-coil kit for head bolts going into aluminum motorcycle blocks.