Ballast

[cab13367]

JGP,

See the link below to some pics of the Gravity III manifold.

https://forum.moomba.com/showthread.php?t=5725

There is one fill pump and three empty (evac) pumps on the gravity III system. There is a drain fitting (and a hole in the hull above the water line) for each bag. You are right - the three bags do not fill at the same rate so I fill them all full. That's the only way to know for sure that you've got them equal. So buy the right size bag and fill them all full each time you go wakeboarding. Water will come out of the drain fitting so you will know when they are full. I have the same set up as the 2007 LSV - 3 x 400 lb bag - and the wake is sweet f(for my ability) and the boat rides great (no poirposing or bouncing). I don't think that plumbing the rear bags to the front bag evac pump will work too well since the water from the rear bags has to get there by gravity, not to mention how long it will take to empty all three bags.

I had the dealer convert my system from Gravity I to Gravity III at the time of purchase. They charged me the same as if I had ordered this option from the factory - $795 - which I have learned from this forum was a great deal.

Al

[JGP54321]

Thanks for the help, but by those pictures I'm a little confused. I'm almost positive that manifold is the fill manifold correct? My fill pump is the same as that and goes to the same location above the transmission but what are those three pump looking things? Are they just strainers or what. They look like additional pumps and its confusing me.

Also, when you talk about the drain holes that go through the hull, is that one for every bag or how does that work. I understand there is an individual drain pump for each bag but it seems like a little much to have to drill 2 more holes for each of the back bags. And it doesn't hurt the drain pumps to have water pushed through them when they aren't turned on and the bags are overflowing.

Another question, (sorry for all these just want to know eveything) is there any EASY way to fill each bag individually without drilling anymore holes through the bottom of the boat?

Thanks,

Joey

[deeluk]

Those pump looking things are solenoids valves. Just like the ones in your sprinkler system. They allow you to fill each bag independently. They're tied to the fill switches on the dash. The pump is activated when any one of the switches is on. Each switch controls one solenoid and allows water to flow to one bag. So, if your bags are different sizes, you can turn off the flow to that bag while still allowing the other bags to fill. Hope that makes sense.

For emptying, you do need a separate hole for each and a pump. I suppose you could tee a couple of lines together somehow and empty out of the same hole. But I bet you'd start draining one bag into another.

You don't need an additional thru hull hole to add the rear bags. You just need to add the solenoids, switches, and plumbing for the rear bags (for filling). And then a pump for each bag, plumbing and holes for draining.

[cab13367]

JGP,

Looks like deeluk answered your questions so hopefully, you now have a better understanding of what is going on.

Regarding your reluctance to drill additional holes for the drain fittings, it's really not a big deal. It's above the water line, and the hull is only about 1/4" thick where you would be drilling. I just replaced my plastic drain fittings with SS ones so I have three of them that you can have - just pay for the shipping.

Al

[JGP54321]

Awesome, thanks alot guys. Think I've pretty much got the hang of what I need to do now I just have to figure out where to get everything but I've been searching online and I think I have a handle on that too.

One quick question though. I love the idea of having the solenoids to fill each bag individually, but I don't really like the idea of having every compartment open to see when they are full. Is it safe to have them overflow like you were saying, forcing water through the drain pumps each time you fill them up? I would think it would cause a good amount of stress not only on the pumps but the entire system? Would this cause a problem or nothing to worry about?

Thanks again fellas

[deeluk]

I don't think it's a problem to overfill the bags and let them start squirting. Happens to me almost every time I go out. I even use it as an indicator that the bags are full. Depending upon what I have in the back compartments, I do sometimes drain the bags down a bit to allow them to close again. Same for the front. The front one will pop the compartment open if you go too far with it. On my boat at least ('04 LSV). I try to finesse that one and stop it before that happens. The rears I usually just let go until they start peeing.

One thing that is good to do periodically is burp your bags. For the front you have to remove it and squeeze all the air out. The rears should have drain caps. If you put the bags in upside down, you can use them to get the air out of the bag. They seem to get some air in them while trailering. If you have too much air in the bags, you won't be able to fill them as much and hence won't get as much weight in them.

[JesseC]

Some people including myself have seen stress related issues with the evac pumps when they have received too much pressure. I do not know if it is just my luck, but I have had two of them crack at the base and begin leaking. I added a vent/overflow valve to my fly high sacs. This stopped the overflow pressure issue and gets the air out of the bags everytime automatically. However the only problem I have seen is that the evac pumps like to cavitate, not sure if this problem existed before, but starting the evac pumps while underway seems to solve the issue.

Overflow line on third fly hig fitting with one way valve:


Rough scematic of my setup: