Cabelas has a nice short booklet on downriggers - only about $10. I got a couple used electric cannons specifically to target Kokanee. But they work great getting down to Trout or other fish chilling in the deeper waters - but the finder is key. Both to locating the depth, and watching your bottom.
Trolled Porcupine - depths down to 100 feet, and up to 10 feet towards shore. The beauty is you send it to the depth you want - you’re not guessing factors of line-length, weight, speed - etc.
I was able to confirm the depth reading as I watched the rigger bar bounce. Never snagged the ball (though you can get a snubber for the weight) but I did lose some jewelry! Weights come in different colors and shapes too - some will bend so you can do like a dipsy, and have it plane away from your boat.
First tried lead lines with pop-gear. Found I couldn’t even feel the rainbows at Hyrum with all that other weight. Great thing with the rigger setup - you can put the pop gear on the weight, then when your line releases it’s all fish. Plus you can use lead line, or regular line. You can also double-stack lines on a single rigger - hit two different depths.
A good downrigger rod helps - Ugly Sticks/Cabelas brand - you want a long rod - bendy tip, but a firm backbone. Rod bends DOWN toward weight, then POPs up - usually hooking the fish for you in the process, when it releases. Rubber snubbers can help keep from ripping Kokes soft mouths.
But I’ve even used them at Willard in 25 ft of water - can hold down at 15 - steady - right through the schools.
I’d highly recommend the electric option - just handling the rod/motor switch, and driving the boat all at once can get tricky. Cranking a heavy weight up and down can wear you out - plus call for that third set of hands…(now if you’re kicking . . . )
But I need a shut-off-switch! I’ve hit the “down” button accidentally and backspooled the wire - what a pain!
I’ve heard the horizontal spools may be more inclined to tangles than the vertical ones.
They do hum, and there can be electrical “charge” issues to contend with - if you get fancy and go with a “black box”. Plus it’s one more thing to get tangled, mangled, and discombobulated - but they do get you down, accurately, and provide options to add more fish-attraction.
Attached is a photo showing the cannon - the white ball in the silver basket is the weight. Ugly stick in the rod-holder, and another rod holder mounted in front (stacking). The DR is on a Gimbal mount that sits in a rod-holder I installed in the seat bench. Whole thing slides right out. I could post more detailed pictures if anyone wants.