|I thought this was pretty ingenious but tell me what you think. The system uses two attwood 750 gph pumps. Sorry my drawing is very messy. This is filling a 600+ pound sac in the floor but could be used in other applications. The slope of the hull makes the burp valve the highest point. Basically the water intake for the engine has a large scupper on it already. This will easily prime the fill pump and fill very fast when moving(the sac has to be a 3 hole but can be a 2 hole using a diverter though)and has a shutoff valve just in case. There is a one way flapper in the fill line to the sac. The drain line comes off the bottom of the sac to a second pump then out the existing bilge line. The burp line ties into the line heading to the bilge line. It must tie in after the drain pump. Put in a one way flapper valve on the burp line just before you tie into the line headed to the bilge or even use a "T" on the drain pump output side. By doing this, the water from the burp functions in two ways: |
1. It will tell you when the sac is full because water will squirt out the bilge output line on the side of the boat.
2. It will fill up the line (through the drain pump) between the sac and the bilge line making doubly sure to prime the drain pump. By doing this you can move the drain pump farther away from the sac and remain primed. Sac will have to be full if the pump is farther away though.
Sorry so long but what do you think?
|I had the exact same idea when I did my system. Here are some tips for ya. Put the drain pump directly to the sac. It will eliminate the priming problem and will run much more efficiant. as you drive around your drain pump will loose its prime. Trust me it will because mine did. All it takes is one air bubble to stop the flow and you are screwed because the pump will stop pumping water. Also put your fill pump as close to the scupper as possible. It will help it work better. The scupper is a great idea. I put one on my boat and It primes so fast it is scary. I can actually fill my sac by just going forward and letting the scupper scoop and force the water thru the lines. One last hint, the use of a one way valve does not always work. I tried it and the force the attwood 750 put out was not enough to open the valve. If you have any questions just email me. It took me 1 month to get my ballast system to work perfectly and I started with the exact same plan as you. I hope this helps. |
|I like it. Low cost yet high flow pumps. Centrifugal pumps have the ability to have water pushed by them by the scoop-type scupper so you can get greater than rated flow on fill pump. Overflow/vent should solve the excess air problems some have complaned of with hippo. Overflow also gives an elegant solution to the worry of exploding bags. |
I would give thought to one defenite change, one possible change, and one nagging concern.
Defenite change: I assume your check valve in the fill line is to keep air from feeding back into your engine raw water pump. You will also need a solenoid-operated valve (like a sprinkler valve) after your pump because at high speeds, pressurized water from your scupper will flow past a Mayfair or Rule pump even if it is off.
Change to consider: Sharing the engine's pickup is a good idea in that you save the cost of a scupper and, more important, another hole in the bottom of your boat. I do have the concern that if your fill line check valve failed, your pump cracked, or had a hose or fitting fail anywhere on that suction line, your raw water pump could suck air. That would stop cooling water to your engine and leave your temp pickup in air. There's a good chance you would never know you were overheating until you heard bad things from your engine. I was thinking about a $25 1 1/4" brass scupper from Boater's World with a brass tee on top of it with two bushings down to two 1" or so ball valves. Yeah, one more hole in your boat, but plenty of water for any bags you will ever put in and you don't put your motor at risk. You could also then do away with the check valve in the fill line.
Nagging concern: Some very smart people have looked at centrifugal pumps and ended up using $200 plus jabaco self-priming pumps anyway. Smart people don't spend more than they have to yet make-a-wake and MasterCraft use the jabscos. It makes sense that the very nice make-a-wake systems would use self-priming pumps because they have no control over installation and want to make a system that anyone can install and still work have it work well. I can also attribute airlock problems with early MasterCraft systems to installation problems. Even so, there's that nagging concern . . .
|Good points. Thanks for giving feedback. One thing I was thinking about was to put a ball valve directly on the t form the water intake and was thinking about another on the sac just in case. Filling could also be done with the engine off as the fill pump is below the water line. If I t into the raw water scupper, it will be right on top of it, basically on the hull. What do you think? One other question, what about losing the raw water pump altogether? Granted you could not fill when the engine is off.|
|I've got pretty much the same set up too. I teed off my engine intake, have a pvc ball valve, to a a mayfair 1100 gph with a brass check valve. I use the attwood 750 to drain and have that teed into the bilge line. |
My fill time is pretty slow and I can't fill while moving. I have another attwood 750 I'm gonna use next season and see if that speeds it up and will stay primed while moving. I have no problem emptying and it only takes a few minutes.
When filling will your pump push anough water out of the bilge line to let you know when it is full?
|Ty, I've actually never have used the drain pump as an over flow. I run a 600 lb sac in the bow area, so I can see and feel it, I just cut the pump when I see that it's full. I'm pretty sure that it could flow through the drain pump if needed, but I've never had to rely on it. If my boat wasn't put away for the winter I go out and test it for you. |