Ever since we originally pioneered a number of upgrades to the factory ballast system in 2002-2008 Supra & Moomba boats we’ve had hundreds of customers that we’ve helped solve the many frustrating aspects and limitations of the Gravity III ballast system installed in their boats. Based on our experience we regularly have boat owners ask us for their options for fixing what is essentially a broken system. Based on that demand we’ve decided to write a number of blog posts, this one being the first, that will take you from the planning stages all the way through the installation process. So if you’re fed up with slow fill times, tempermental draining, and a wakeboard ballast system that basically doesn’t work, read on for the solution. If you have any questions at any point in time feel free to contact us.

What’s Wrong?
There are three main issues with the factory Gravity III system Supra and Moomba installed from 2002-2008 (the ballast system was essentially identical throughout this entire process, with the exception of bag sizes, which vary by model and the day of manufacture):

1) Slow Fill Times: This is a result of the fact that the factory system uses a single Rule aerator type pump to fill from one to three bags depending on how many switches you turn on at one. Additionally, the system uses solenoid valves designed for use in a below ground irrigation system to control the flow of water to each of the three bags. That means when you turn on the fill switch for a particular bag the system is engaging the fill pump AND opening the solenoid valve to that bag. The more bags you try to fill, the more the longer it’s going to take as the output of the single fill pump is routed to all three bags by the solenoid valves.

Additionally, the sprinkler valves are designed to maintain pressure (which is important for an irrigation system with retractable heads), but decreases volume significantly (which is what we’re interested in for a ballast system). Removing the sprinkler valves would increase the speed of the system by close to 50%, but would sacrifice the ability to control which bag is filling because any time the fill pump is on it would be sending water to all three bags.

2) Inconsistent Draining:  The factory system has an individual Rule drain pump for each bag.  Because aerator pumps are not self-priming it is crucial that the drain pump be mounted in close proximity to the bag it is draining (we prefer to have the pump mounted directly to the bag).  The Gravity III system has the pumps for the rear bags mounted approximately two feet away, which was down to preserve the appearance of the installation.  While it certainly is nice

3) No Vent Connection:  In the factory configuration there are only two connections to each ballast bag; one for filling and one for draining.  While the drain connection can act as an overflow to prevent damage to the bag or boat if the fill pump is left on too long (a common occurrence due to the slow speed of the system), because it is connected to the bottom of the bag it does not allow air in the system to be vented.  That means the bag can have a significant amount of air trapped inside of it, which will limit the capacity of the bag.  This is especially a problem for the center bag, but can occur with all three.

What’s The Fix?
Although the specifics can vary depending on goals, budget and time, there are basically two methods of upgrading the factory system to correct the issues outlined above:

Option 1: Upgrade to reversible flexible vane impeller pumps (Jabsco Ballast Puppy or Johnson Ultra Ballast) which is the route Moomba and Supra have chosen for 2009 and newer boats.  The advantage to this layout is a drastically simplified system with far fewer components, less hose, and a dedicated vent on the top of the factory bag.  Additionally, with one pump connected directly to each bag in the system, fill and drain times are reduced significantly.  The disadvantages to this layout are that it requires the installation of two new thru-hull connections for the additional pumps, and flexible vane impeller pumps are significantly more expensive, so the complete system ends up costing around $900.

Option 2: Install additional aerator type pumps (like Attwood’s Tsunami 800) along with additional hardware resulting in an individual fill pump for each of the bags in the system.  This setup also provides an individual fill and drain pump for all three bags, and does not require the sprinkler valve distribution manifold that is present in the factory system which further increases speed.

This configuration does not allow for a dedicated vent connection off the top of the bag, which is the only real disadvantage.  It’s also significantly cheaper to install this system than the flexible vane impeller based option above, but there is more install work to be done.  The parts for this upgrade total around $300 without the vent connections, or $400 with the hardware to connect a vent line to each bag (which requires bags with three ports on them).

You can view one of our customer’s installation summary on the Supra Boat owners website here.

Other Options
If you are content with the speed of the system and just want to enlarge the capacity of the bags for surfing or wakeboarding we do offer a factory upgrade kit for 2002-2008 Moomba and Supra wakeboard boats which includes everything necessary to replace the rear ballast bag with a larger capacity model (up to 1,450 pounds).

If you have any specific questions about upgrading the ballast system in your Supra or Moomba, feel free to contact us via email at sales@wakemakers.com or by phone at (888) 338-6085.