the company is phantom enterprise inc. there out of bissnes scine 2006. it is a '15 1980 phantom boat in case you can tell me the person or motor rating

the USCG guidelines for boat builders calculates max HP as 90 subtracted from twice the length times width (at the transom), rounded up to next multiple of 5.

max for a 15' boat with a 5 1/2' wide' transom would be 15 x 5.5 x 2 = 166 minus 90 = 76, rounded up to 80.

a boatbuilder can choose to use a lower maximum, or a higher maximum if they can pass certain performance tests.

the formula is different if the transom height is less than 20'' or for tiller steering.

it tells u in here how to figure ur weight & persons capacity but it involves sinking the boat:
http://files.dnr.state.mn.us/education_safety/safety/boatwater/backyardboatbuilders.pdf

Here is 1 50hp web search the boat>
http://bigbendsportsman.com/member_photo_galleries/ken_owens_boat.htm