Can this product be used to stop leaks on aluminum boats?

I wouldn't trust this material to seal a leak in a boat. If you talking about using it between aluminum parts on your boat which have been riveted in place and you plan on drilling out the rivets, then reassembling using this as a gasket material, it might work. You might check in the paint department ... Rustoleum (and there might be another mfg. too) has a spray sealer which you can use to build up a watertight seal. I used some on a plastic bucket with a crack in the bottom, about 4 coats sealed the crack ( 1/8" wide in places). Filled the bucket .. no leak or drips.

Yes, temporary. Surface needs to be clean and dry.