What does it mean when a trolling motor says 40 lbs thrust

What it it only pushes 40 lbs?  My son weighs more than that

Someone please define this for me  :-[

Here are some FAQs to help answer your question

http://www.minnkotamotors.com/support/faq.asp?pg=general&lp=gb

If you were to take a 40 lb weight in your hand and hold it up against the force of gravity that is 40 lbs of thrust. Take the same amount of effort you put in to holding up the weight and push your boat away from you or the dock. That should be a rough translation.

So yes, 40 lbs of thrust is adequate for most boats under 18 ft depending on weight, wind, draft and other smaller variables.

Disclaimer: Thats my opinion and someone on here will be along shortly to tell you to get as much thrust as you can afford. ;D  and that not a bad idea either.