Can anybody help me with trolling?

My family is borrowing a boat and I want to
fish for big trout but we dont have a downrigger and my dad says to just tie a weight to the line just above the plug.

Does this work?Any suggestions?

Your dad has described the "poor man's trolling rig". I've tried it and it does work. You take a weight and tie it to a line. Off of the weight you tie your downrigger release (have a couple feet of line connecting the release to the weight - don't tie the release right to the weight). You then attach you fishing line to the release like you would with a downrigger. Set the drag, put the rod in the rod holder and slowler lower the "downrigger" line into the water. I used water-proof marker and marked the line at 5 foot intervals. When you get to the depth you want, tighten your drag, secure the rigger line and you are fishing. Be sure to not get the rigger line all tangled when you pull it up. I wouldn't use much more than 5 pounds of weight. This set up works good for lake trolling and shallow salt water trolling.
Good luck!

You could buy some Lead Core line for 15$$ at any tackle retailer, it gets you down about 30 feet easily, the slower you go the deeper it goes, it is color coded so you can sort of know how deep you are, after 30-40 feet it just plains off flat though, I've caught some big'uns on my lead line.

Used a little laker dowrigger for years and it was only $40. Used a 6lb weight and I caught fish from both my canoe and little powerboat. Moved up to an 18 footer and a Penn 600 downrigger three years ago. If you have a little boat, 10-14 foot rowboat, the little laker works okay. You could pick up a used boat for about $200, add a trolling motor for another hundred, then the downrigger with all associated rigging for about $75 and you have a poor mans rig that can catch all sorts of fish from. Maybe this is a bit overboard, but that's how I started fishin' deep with consistency. I got all of my gear used, except for the Little downrigger. A