I was just wondering if anyone knew the formula for finding out what the weight limit or HP limit is on a boat that doesnt have  plate.

One of the best ways is find someone with a similar boat in bottom width, length, beam, construction, and side height and base it off of that.

I think in some areas you have to have it calculated and a "work sheet" needs to be made using complex calculations and a formula. You might want to look at the United States Coast Gaurd website and snoop around and maybe call someone who can calculate it for you. Maybe Marine Patrol will do it.

You can find the regulations through the coast guard, every manufactured boat has to be tested by them.

I had this problem when I tried to register an old boat in a state I just move too.  I had to get a form from the PA Fish&boat Commission.  Then complete all the measurements and send it in to them.  They sent it back with a plate that hat all the specs on it as far as HP limit and weight restrictions.  

Check on your state's boat registration web site to see if they offer such a form/service.

I think it cost me $10 or less.

Cool thanks guys