Water Ballast pump out

[walt]

Tom, your number of .3 psi sounds about right for 8 inch depth of the water ballast tank. I assume it’s based on the way a mercury barometer works (replace mercury with water) which is the model Viswiz used. I think the actual depth of the water ballast tank might be closer to a foot but the pressure required to hold out the water would just be scaled by 12/8 - still only .45 psi. How fast the water gets pumped out depends on how much over the .3 psi the pump is.

Interesting that the factory tests the tank to 2 psi. One time I was getting the 26S ready to take out and set up my 12 volt mattress air pump on the ballast tank (I think its rated for just a little over 1 psi), turned the air pump on but forgot to open the bottom valve on the ballast tank. I went and got the truck/ trailer and then came back to the boat. The pump had put what seemed like a LOT of pressure in the ballast tank. It was enough pressure that I was worried about damage... However, I have used the boat many times after including last week and it seems no issue at all. My pump can’t even get up to 2 psi.. so knowing the factory tests to 2 psi is making me even more comfortable.

Good to know in case you do something dumb like I did with blowing the ballast and forgetting to open the bottom valve. FYI, my air pump uses about 8 amps or so while blowing the ballast but it only takes about 10 minutes or so. Blowing the ballast makes getting the boat on the trailer (and in the right spot on the trailer) easier..

[133bhp]

anyone got a vid of this in action?

[gabid]

Thanks for sharing this info, guys. I never thought that a small mattress pump will do it. It make sense, the pressure required is only the weight of column of water from the transom valve to the surface.

[budgates]

Im just curious, does the 26 not have a swing keel? I just got a venture 25, it has no ballast tank, but it has the swing keel figure if (when) I run aground on something, ill crank the keel up & float away.

The difference between a M26 swing keel and a M25 swing keel is that the M25 uses a heavy keel for ballast and limiting leeway where the M26 uses a light keel (or daggerboard for the D & M) for leeway and a water tank for ballast.

[OverEasy]

What a nice thread of thoughts went into this topic!
I had a great laugh at myself discovering that I had reinvented the wheel, yet again!
I had been concerned about being able to dump ballast and explored various approaches such as mounting a ballast pump inside the tank, mounting an adapter to the exit drain amongst others when after about 15 minutes had a “Eureka” moment and decided on a low pressure air pump hooked into the ballast tank air vent via a side tee fitting —- the through straight section for normal venting with the compression plug and the side tee for the low pressure air supply from an old 12 Vdc air mattress pump that maxes itself out at maybe 1 psi before it stalls out. More than enough pressure to blow out the ballast and not enough to pose a problem is the drain is shut.

Then when feeling all good about my creation I got that this was something that must have been done before and sure enough I was at least 7 years behind all the really bright bulbs on this forum!

Being a newbie to a MacGregor I can really appreciate all those really creative and thoughtful members who have been ready willing and able to discuss, evaluate and share their experiences!

[Jimmyt]

What a nice thread of thoughts went into this topic!
I had a great laugh at myself discovering that I had reinvented the wheel, yet again!
I had been concerned about being able to dump ballast and explored various approaches such as mounting a ballast pump inside the tank, mounting an adapter to the exit drain amongst others when after about 15 minutes had a “Eureka” moment and decided on a low pressure air pump hooked into the ballast tank air vent via a side tee fitting —- the through straight section for normal venting with the compression plug and the side tee for the low pressure air supply from an old 12 Vdc air mattress pump that maxes itself out at maybe 1 psi before it stalls out. More than enough pressure to blow out the ballast and not enough to pose a problem is the drain is shut.

Then when feeling all good about my creation I got that this was something that must have been done before and sure enough I was at least 7 years behind all the really bright bulbs on this forum!

Being a newbie to a MacGregor I can really appreciate all those really creative and thoughtful members who have been ready willing and able to discuss, evaluate and share their experiences!

Low air pressure is definitely an easy way to get a lot of it out. The 2psi factory ballast tank test gives some confidence that the ballast tank will take a 1 psi air purge. The seams on the low side probably experience about 1 psi of water pressure when heeled over hard anyway (I believe Tomfoolery brought this up before). So, as long as the air pump won't make over 1 psi, it's probably fine.

My only question would be, how much water remains in the tank when the water seal vanishes at the rear valve opening? If significant, would a positive displacement bilge pump with a low intake be a better way to go?

I purge mine with a 60hp outboard, currently. But it is a topic of interest; possibly a future mod...

[Ponaldpe]

My only question would be, how much water remains in the tank when the water seal vanishes at the rear valve opening? If significant, would a positive displacement bilge pump with a low intake be a better way to go?

If you close up the fill valve when it starts to bubble you can get almost if not all of the water out.

[OverEasy]

Hi! Good observation and thought!
That was my assumption in that I can adjust the opening height of the ballast drain get valve low to get as much of the water out as possible for the least amount of hassle. The gate valve has a variable opening of about 2 inches so lowering it will drive the in ballast tank “air bubble” lower pushing out that much more water. It’s likely that I’ll be standing at the rear watching the bubbles anyway and that should also help lowering the stern getting more water out.

The low pressure mattress pump at 1 psi won’t over pressure the ballast tank if I fumble and close the gate valve prematurely, or if there is a delay between closing the valve and turning off the air pump. Once the pump is off I would make sure to equalize the tank vs ambient air pressure.

I figure that the removal of water with this air pump approach would be equal to that of getting the boat up on plane with the outboard to drain the tank. The advantage is I can do it standing still.

( The other advantage (which I can only hope never happens....) is I can lose ballast on demand if I run aground while motoring with the centerboard up. ) Not that the estuaries around Beaufort SC are shallow or have variable tides or moving sandbars or stuff like that...eh? .