Bongo Fury

So I think one of my issues is my alternator is going. I took the belts off and spun the wheel on the alternator and it makes the grinding noise I can hear when engine is running.

Going to replace it with a bongospares one..

My question is, when I put it back together the two belts go around shaft, water pump and alternator..
how tight should they be?
I see people say to set the tension to the recommended setting, but no idea what that should be...
also i have no special 'torque' tools.

secondary question.. why are their two belts.. they seem to be the same function?

also.. is there any special timing/marks/layout of the belts i need to ensure?

Thanks again for excellent support

The deflection should be (from New) between 7 and 9mm.

You don't need the torque gismo to set the deflection.(use your fingers)

No timing marks required.

Two belts are fitted for (backup and balance).