I've used battery boxes with panel mounted SAE two-pin connectors for many years.  It's convenient to be able to plug the battery into my fish finder when fishing and then plug it into a charger after the trip without ever opening the box.  The boxes are inexpensive but effective "Outdoor Products" dry boxes available at Walmart. The wiring between the plug and the battery includes a fuse holder. I use the strap to fasten the box to the mast holder inside the front hatch of my Hobie kayaks, and it also provides a handle for carrying the box.

I ended up having the 4 ratcheting straps and 2 sailboat sheets each go up through one drain hole of the kayak, then come down through another drain hole; both ends then hooked on the truck's anchors. To be extra safe, I used 2 ropes to tie the front handle to the front bar of the truck rack. This way they won't slip back for sure.

Don't use racheting straps to tie down kayaks.  They put too much stress on the kayak's hull, and can damage it. And especially don't run racheting straps through the drain holes of a sit-on-top kayak.

Electric reels? How soft and degenerate are kayak anglers getting?  What will be next - electric motors on pedal kayaks?

I used to lift my kayaks up to the ceiling in my garage with a primitive lift system involving ropes held by cleats on the wall of the garage.  I would lift up one end of the kayak several feet with one hand while pulling on the rope with the other hand and then cleat the rope, then lift the other end of the kayak several feet with one hand lwhile pulling on the rope with the other hand and then cleat the rope, and repeat that process on alternate ends of the kayak until the kayak was up near the ceiling of my garage.  During each lift, only my hand on the rope was keeping the kayak up.  During one of those lifting jobs the rope slipped out of my hand and my 13' Ocean Kayak Trident fell down and bashed me on the head. The other end of the kayak swung up and hit the ceiling, the leverage of the falling kayak straightened out the O-bolt which held the rope, and the whole kayak came crashing down on the floor of the garage.  I didn't get knocked out, but was somewhat stunned.  The kayak was fine.  Shortly after that incident I bought a Garage Gator electric hoist for the kayak.  https://proslat.com/collections/storage-elevators.  Those hoists are moderately expensive, but it's delightful to hit the "up" button and have a kayak effortlessly levitate up to the ceiling of my garage.  I now have three Garage Gators.

Bluestar, you can fish in a lake or the ocean from a whitewater kayak if you have a solid roll and other whitewater skills, but it's really inconvenient.  I've been a whitewater kayaker since 1985, and I do some fishing from a whitewater kayak.  See, for example https://www.northwestkayakanglers.com/index.php?topic=13913.msg151981#msg151981 and https://www.northwestkayakanglers.com/index.php?topic=14090.msg153356#msg153356. Where are you going to put your rod when you're paddling? If you have a whitewater kayak which you're only going to use for fishing, you can mount a flush or above-deck rod holder someplace on its front or rear deck where the rod holder and/or the rod won't interfere with paddling.  Otherwise, you'll need to break the rod down, pop off your skirt, and stuff it inside the kayak, or perhaps stick its butt down inside your PFD.  You probably aren't going to mount a fish finder on a whitewater kayak.  You'll need to bungie a net onto the deck of the kayak, because popping your skirt to get at a net stowed between your legs is dangerous while you're playing in a large fish.  Any fishing gear and fish will need to be stuffed down between your legs. Whitewater kayaks aren't very stable, and rely on paddle bracing to stay upright, so when you're fishing you'll probably need to lay your paddle across your spray skirt so you can drop your rod (hopefully not in the water) and grab the paddle if you get tipped and need to brace to stay upright. And if you catch a large fish, staying upright while playing it in without being able to use your paddle to brace will be a challenge. And if you swamp or swim out of a whitewater kayak when you're away from shore, you can be seriously screwed.

A paddle sit-on-top fishing kayak is way better than a whitewater kayak for fishing.  Sit-on-top fishing kayaks are fast and stable, and you can easly mount a fish finder, rod holders, a net, fishing tools, a cooler, a downrigger, and other fishing equipment on them or inside their hatches.  You can turn sideways in your seat to get at equipment in the rear cargo area.  You can clip your paddle into a paddle holder and fish with confidence in the stability of the kayak.  If you tip a sit-on-top kayak over, you can right it and climb back on top of it in seconds; sit-on-top kayaks are safer than sit-inside kayaks for that reason.  If you want greater control over a paddle sit-on-top kayak for surf launches and landings, you can add thigh straps to the kayak. Because nylon thigh straps are a hook magnet, I un-clip them and stow them inside or behind the seat of my paddle sit-on-top kayak while i'm fishing.

Pedal sit-on-top kayaks are way better than paddle sit-on-top kayaks because you can pedal around in the kayak while fishing with both hands, eating lunch, putting on sun tan lotion, using your phone, etc.  You can also point a pedal kayak's nose into the wind and/or current and pedal to hold yourself stationary over the bottom while fishing with both hands.  I do virtually all my kayak fishing from my two pedal kayaks.  My 13' paddle sit-on-top kayak languishes in my garage, and I only use it for river fishing and for snorkeling and speargunning for pike. You can add thigh straps to a pedal sit-on-top kayak for use when paddling it during surf launches and landings, although you obviously can't use thigh straps while pedaling.

If you want to start kayak fishing in lakes or the ocean, I recommend that you demo some pedal sit-on-top fishing kayaks, and then buy a used or new one.  Pedal sit-on-top kayaks are by far the best platform for lake and ocean kayak fishing.

While searching the internet for something else entirely, I stumbled on the worst designed "kayak" I have ever seen: https://lightasairboats.com/products/unchartered-watercraft-scorpion-fx?currency=USD&variant=39427198451796&utm_medium=cpc&utm_source=google&utm_campaign=Google%20Shopping.

I have a couple suggestions from another universe of fishing - ice fishing, which is what I'm currently doing, because I live in Montana - and from hunting. 

I haul my ice fishing gear around on the ice, often for long distances.  I attach a long loop of 3/4" soft polypro rope to the front of the sled, stand inside the loop, and use it to pull the sled, as shown in the picture below.  This is simple and convenient, but a disadvantage of the loop of rope is that it rides at the level of the ball of my hip joint, i.e. at the point that the top of my thighs meet my hips, which isn't particularly comfortable, and I have to hold onto the rope lightly with my hands to keep the rope from sliding down. If I come to a steep downhill when getting to a lake, I lift the loop of rope over the sled, stand behind the sled, and use the loop to keep the sled from running away downhill.

When I'm hunting, I bring along a length of climbing accessory cord tied to a loop of 2" webbing.  When I shoot a game animal, I tie the accessory cord around the animal's neck, step into the loop of webbing, pull the loop up to my hips, a start dragging the animal towards my vehicle, which can be a huge amount of work, particularly if there isn't any snow on the ground to reduce the friction of the animal.  But a disadvantage of this system, like the rope which I use to pull my ice fishing sled, is that the loop of webbing rides at the level of my hip joint and can be pretty uncomfortable, particularly after a long haul.

I can improve the comfort of both of these setups by buckling a padded waistband from an old external frame pack around my waist, and clipping the ice fishing sled or the game animal to the waistband with a carabiner.  The waistband has three advantages: (a) it's padded, and thus more comfortable; (b) I can cinch it around my waist so it sits at the level of the top of my hips, which is a lot more comfortable than riding at the level of the ball of my hips; and (c) because I can cinch it around my waist, it doesn't tend to slide down, so I don't need to hold it up with my hands.

I launch my 12' Pro Angler 360 kayak from a lot of unimproved launch sites, some of them with steep gravel beaches.  It takes a lot of effort to pull that mini-bass-boat up from the shoreline, and the padded waistband really helps.  I have discovered (a) that I need a cart which is high enough so I don't drag the stern of the kayak on the ground when I'm pulling the kayak (I use a Wilderness Systems heavy duty kayak cart with beach wheels), (b) that the rope between the kayak and the waistband needs to be short enough so the bow of the kayak can't drop down onto the ground, (c) that the rope between the kayak and the waistband needs to be long enough so the bow of the kayak doesn't bang into the back of my legs when I walk, and (d) when going dowhill I need to be able to use my hands to hold the bow of the kayak against the back of my hips to hold back the kayak, or better, I need to be able to quickly detach myself from the hauling setup, go around to the back of the kayak, and walk it down the slope while hanging onto the stern.

I hope that these descriptions will help 123 engineering come up with a system for hauling his kayak.  I think that a padded waistband will be more comfortable than a rigid bar.  Another option is to buy a game hauling harness or deer dragging harness and use it to haul the kayak.

Just curious how deep anyone has been able to troll with the Scotty Laketroller. I'd think it would be difficult to go down  below about 50', whereas the Depthmaster can go to virtually any depth. Of course, it's no fun to crank up a 6 pound (or heavier) ball from the depths, but on a Hobie, it does provide for a full-body workout...

When downrigger trolling, the maximum depth that you can see your downrigger weight on your fish finder before the weight gets blown back behind the cone of your sonar depends on (a) the speed at which you're trolling,(b) the weight of your downrigger weight, (c) the amount of drag created by your lure, (d) the amount of drag created by your steel downrigger cable or braided downrigger line, and (e) the width of the cone of your sonar (i.e. the frequency setting).  When trolling at about 1.5 mph with a four pound weight on a Scotty Laketroller, using a low drag lure and 175 pound low drag braided downrigger line, and with my fish finder on a wide cone setting, I can see my weight down to about 70 feet.  When trolling at the same speed with an eight pound weight on a Cannon Laketroll, using the same lure, braided downrigger line, and fish finder settings, I can see my weight down to about 220 feet.  But with either downrigger, if I go faster and use a high drag lure like a Flatfish or Kwikfish, my downrigger weight will disappear from my fish finder screen at a much shallower depth.