I posted this on Northwestkayakanglers.com a couple months ago and realized the Hobie forums would probably like to have it. Hope it helps!
The system works just fine as-is, but I felt there were a few ways I felt it could be improved. Lets start with the easy stuff.
I added new eyelets to the inside walls of my gear well for the straps to clip on to. I like still having the gear well bungee straps connected while the tank is in the gear well since they come in handy when storing things around the side of the tank. I positioned the eyelets so that when the straps are clipped on, they are straight up and down. This provides maximum holding strength while the tank is sitting where it needs to be. I was careful to have the eyelets positioned so that both the intake tube and the outflow tube fit into the scupper holes while the tank is strapped down tight.
Next comes utilizing some of the surface area of the tank.
I put two eyelets on the lid so that when I have rods sitting in the rod tubes of the tank in storage mode, their respective leashes clip on to the tank and are not stretched from the cockpit area.
I installed a doubled length of bungee on both sides of the tank so that I can store various items on the outside of the tank. One end of each bungee runs through an eyelet and the other end loops around a bungee post.
Now comes the tricky stuff.
I had developed a few goals I wanted to accomplish after doing lots of research around the web of issues that other users of this system had encountered. The first thing that came to my mind when I started tinkering was I wanted to extend the battery life. I feel it is unnecessary for the pump to be running constantly when live bait is in the tank. And of course, 8 hours would suffice for most trips I take, but if I take a weekend trip somewhere and am fishing for multiple days, I don’t want to worry about my battery dieing after the first day. Second, I wanted to keep the pump from sucking up everything that comes close to the intake. Third, I wanted to have water stay in the tank when I shut the pump off. A modification needs to be made for this because when the pump is turned off, the impellers of the pump stop spinning around to force water through and thus, an open path for the water to escape is created. To meet these goals, I added three important components to the system.
The first component I added was a waterproof electrical timer switch. I had this switch from my days working for Anglers Yak Shack but you can find them around the web for around $40. I wired it in series between the switch and the pump. The pump turns on for 7 seconds, then shuts off for 21 seconds, giving the pump a 25% duty cycle. While re-wiring the tank, I also greased the hell out of the on/off switch with dielectric silicone grease since I’ve heard it isn’t exactly a corrosion-resistant piece.
After adding just the timer switch, two obvious problems were obvious. After the pump stops pumping, most of the water that was just pumped into the tank flows right back out though the pump. Also, if there’s not enough water in the tank, the pump needs to be re-primed after every cycle. The obvious fix for this is a check valve of some sort. I tried a couple from the hardware store but realized that the pump doesn’t push the water into the tank with the requisite force to open most PVC check valves. This means the check valve needs to operate on the suction force created by water trying to flow back out through the pump. Home Depot has a fitting meant for sprinkler systems that operates on suction rather than the force of forward flow that would probably work, but after trolling the interwebs, I stumbled across this little gem of an idea:My 2 cent Hobie Livewell modification
It seemed cheap, shoddy, and flat out ridiculous, but I had to give it a shot. I slapped on a “Happy Birthday” balloon with a slit in the top from the local grocery store and to my surprise, it worked flawlessly! I added the piece of tubing to the outflow fitting of the pump to make testing easier and have removed it for regular use. However, I found that an extra fittings (pictured below) are needed to get the balloon to function as a check valve. The balloon cannot be simply placed over the outflow fitting of the pump.
Two down, one to go.
I saw somewhere on the internet that someone had put a stainless screen inside the scoop fitting so picked up a stainless steel mesh sink strainer at the local hardware store and cut out a piece I thought would be big enough to fit into the scoop fitting.
After trimming here and there, I molded it around my pinky finger and it fit just right. I gooped the inside of the scoop fitting at the entrance really well and slid the screen into place. Before the goop was set I pushed the screen out a little from the inside to get it to stick out of the scoop a little. When the goop was set, I picked off little chunks of goop that would impede the flow of water through the screen with a tweezers as best I could.
After the goop was dry, I was really anxious to test it out. I was worried that weeds and other debris would get stuck to the screen when the pump was pulling in water and stay there until I cleared them somehow. So to see if this would happen, I filled up my sink with water and positioned the livewell next to the sink so the intake tube was in the water. I found some lettuce in the fridge and figured it would perform well as simulated weeds in my testing. I tore up some leaves into small pieces and threw them in the sink. I primed the pump to get the system going and what happened next blew my mind.
I grabbed a few pieces of lettuce and pushed them up against the intake screen. As the pump came on and started pulling in water, as I suspected, the leaves were pulled up against the screen. However, when the pump stopped, instead of staying on the screen, the leaves were pushed off and floated away. WOAH!!!
It turns out that when the pump stops, the water tries to flow back out though the pump. This back-flow pulls the balloon shut, but before that happens, a very small amount of water does flow back out through the intake screen via conduction. Think of it this way: In this situation, we can treat water as an incompressible substance or as one long connected piece of liquid that fills the pumping path from the intake screen, all the way up to the balloon. So if a little bit of water flows back to pull the balloon shut, then a little bit of water must flow out through the intake screen. Essentially, the screen has a self-cleaning mechanism. Below is a sequence showing the leaves stuck to the screen while the pump is running, the leaves being pushed off the screen, and finally the leaves floating away from the intake.
I repeated this process over and over and could not get the leaves of lettuce to stick to the intake screen. Pretty darn slick! After the sink test, I was confident enough in the system to take it out on the ocean and put it to good use.
I have now used the system several times out on the ocean a variety of places where there is plenty of marine vegetation and other organic debris. The system has not become clogged with debris or weeds and the tank has always been able to fill within a reasonable amount of time. I have not fully measured the battery life yet, but I was able to run it for two long days on the water for a total run time of over 12 hours without a recharge and I did not notice any decrease in flow velocity provided by the pump.
Bottom line, the system works well as it is. But with the additions I made to it, it is truly amazing! Tight lines!