Scoop or flat thru-hull for reversible ballast???

I am getting everything around to install an automatic ballast system in my 1997 Super Sport and I will be drilling a seperate 1.5" thru-hull on the bottom of my boat for the water pick up. The thing I can't decide is what type of thru-hull should I use. . .a scoop type thru hull or a flat thru hull?

This thru-hull is going to go to a manifold which will have 3 reversible simer pumps hooked up to it. I will be filling and draining all from the same thru-hull. If I put a scoop type thru hull in, will it create too much back pressure when I'm trying to empty the sacs? Also, will it create a lot of pressure when I am pulling somebody and the water is shooting in to the thru hull?

If I use a flat thru hull, do you think the 3 pumps would suck the water up enough to not lose any fill time? Thanks for any help.

Also, where is the best place to get a 1.5" thru-hull?

scoop all the way. i installed a pumpless ballast system this fall and i dont have any pumps at all. the scoop fills 1000 lbs in under 6 minutes @ 20 mph. a flat thru hull would probably work but im reasonably certian a scoop type wont limit your flow. i dont clearly understand your question about empyting the sacs. i dont think it would be possible to empty the sacs through the same thru hull as the water pressure would be to great(while moving that is). i installed mine where it was accessible to turn off the ball valve(which was installed for primarily safety reasons but i can also stop all water flow) when i open the engine cover. about 6-8 inches from the center to the boat. if you can predrill with a small bit from the inside itll take alot of the guess work out of where to place the thru hull when youre on your back underneathe the boat about preparing to drill a 2 inch hole thru your hull.

If you use a scoop, just drill some holes in the backside of the scoop so you can still empty at speed, also beware that if you aren't filling/emptying these at the same time your pumps will want suck water or air out of your other tanks/bags instead of out of the water under your boat. Sounds silly but we ran into this problem when developing a ballast system. We tried one scoop then decided to run with three separate small 1/2" scoops instead of the BIG scoop and it works a lot more efficiently. We are now testing some centrifugal set-ups Good Luck

Chris, were you using reversible or aerator pumps in your system? I wouldn't think it would suck water from the other sacs because the other pumps I have would have that sac sealed off. I am using reversible simer pumps, so they shouldn't let any water past unless they are turned on.

We tried Jabso and SCC reversible pumps and had more of an air problem with the Jabsco(the flow a lot but the impeller is a bit loose, which lets air through). A little water transfer isn't a big deal but the air will get in and keep flowing through the vent to that tank and you'll eventually burn up the impeller. We only had this problem when one of the tanks was near empty. It may not be a problem with bags?

I put the simer system in with one big scupper through hull and it works great. The scupper faces forward and fills a bit faster when moving, but will fill or drain while moving or sitting still, and they can all be running at once or just one at a time. I split off to four pumps, one for each side, front and back. I vented each sac through the side so that they don't have any air issues and don't blow up. I havn't had any problems with the bags pulling from each other or anything.

The only thing I am going to change on the next boat is that I am going to put flow switches in line so that you know when the bags are empty - right now, its hard to tell since it emptys through the bottom. Hopefully I'll even get it wired up so that the flow switches trip the pump circuit so that the system shuts itself off... but, I'm not sure exactly how to make that work yet. I'm sure the right person could tell me...

(Message edited by Matt Ostmeyer on December 30, 2004)

The flow switch sounds like a good idea, tell me what you come up with Matt...

For sure - when I get something figured out I will post all the info...

Matt O, can you post info on the flow switch?!

Matt,
Did you get your thru hull online? If so, where did you purchase it from?

Still havn't spent the time to figure out where to get a cheap flow switch... they can be bought from many high-end plumbing/fluid transfer supply warehouses in the price range of $100-200, but those are for very sensitive/very high pressure applications. For a ballast tank, surely there is something out there in the $10-40 range that will get the job done. When I find the one I'm going to go with, I'll post the system for sure.

Justin - I got my thru hull from a marine supply warehouse in Kansas City through a small boat repair shop down the street from me in Stilwell (south side of KC). I think I paid like $35 or $40 for an 1 1/4" scupper. They can be found online too...

flow switches don't work well in practice, no major boat builders use them anymore. It's easier with tanks rather than bags. If you have tanks, you can easily implement a level switch, most are build as gas tanks to start with. If you have bags or tanks, you need free outflow to prevent destroying fiberglass. Flow switches are useless. Tanks with level switches.