Moving mooring weights

[Frank]

I have two concrete blocks, about 250 lbs each, serving as mooring weights. They are chained together on the lake floor about 10 feet deep. I'd like to move them 20 or 30 feet parallel to the shore.

Anyone ever done this? I have a 26' powerboat and a waverunner. I also have two 6' tall strong brothers in town :). Should I try to attach a line to them and tow them with either the boat or the waverunner? What sort of line would withstand that much weight? I have this vision of my wave runner being pulled under by the weight... obviously wouldn't happen with the boat.

Or should I try to somehow manually walk them over - is it possible for my brothers and I to dive down there and lift them and scoot them over a bit at a time?

Thanks for any help!
Frank

[TomC]

you'll never move them with a wave-runner. You could move them with your power boat, provided you could get them off the bottom. there are issues with lifting them up: 1) if the bottom is soft, they may have sunk in, you will be hard-pressed to overcome the suction of trying to lift them. 2) you will probably damage the finish of your boat. dragging a rusty, coarse chain or rope over your gunwales will cause damage (I've done it). Unlikely that someone or a pair of someones lift 500 lbs straight up hanging over the side of a boat anyway.. this process is best done with a barge.

If these have been in the water over 5-7 years or so, and the have any metal hardware (like bolts, hookeyes, etc) as part of the attachment system, they probably should be replaced, due to corrosion. If it were me, I'd make new ones and put them where you want them. Concrete is very cheap...

[Mee-n-Mac]

I have two concrete blocks, about 250 lbs each, serving as mooring weights. They are chained together on the lake floor about 10 feet deep. I'd like to move them 20 or 30 feet parallel to the shore.

Anyone ever done this? I have a 26' powerboat and a waverunner. I also have two 6' tall strong brothers in town :). Should I try to attach a line to them and tow them with either the boat or the waverunner? What sort of line would withstand that much weight? I have this vision of my wave runner being pulled under by the weight... obviously wouldn't happen with the boat.

Or should I try to somehow manually walk them over - is it possible for my brothers and I to dive down there and lift them and scoot them over a bit at a time?

Thanks for any help!
Frank

First let's pretend it's as simple as possible. I believe normal concrere has a density of somewhere between 120 and 150 lbs/ft3. Water has a density of 62.4 lbs/ft3 and so the bouyancy effect means (ideally) you'd only have to exert an upward pull of 120 - 146 lbs to lift a 250 lb block off the bottom. If you could rig a block and tackle to the boweye of your 26ft'er and do 1 block at a time ... it sounds feasible. Now that said what TomC mentions (suction) is probably going to ruin the simple thinking above. Any chance your bottom is rocky ? Might be worth a quick try :coolsm:

[MJM]

If you do try to drag them, you'll need to
1} Pry up the leading edge to break the suction/clear the depth it has settled.
2} Put something under the edge that will allow the block to slide across it easier than a sandy bottom.

I did it once, and used two of those 6ft metal prybars as rollers the block could slide across.

Have fun!

[fatlazyless]

How about using the lifting power of inflating an inner tube tied underwater to the heavy mooring? Bottoms up!

[DRH]

We had our 1,000 lb mooring block moved a few years ago by a diver who used an inflatable air bag designed for that purpose. Lifting and moving the block was easy ... the diver just took the deflated bag down to the block, attached it to the mooring chain, and inflated it with air from his tank. Once the block was lifted off the bottom with the air bag, the diver could move it around and place it where he wanted.

[codeman671]

You could always check with any of the marine construction companies to see if they are pasing by any time soon with an excavator on board their barge. It took only a few minutes to hook onto the chain of mine (2k lbs!) and move it 30 feet over. I can't imagine that they would nail you too bad to make a few bucks if they were in the area anyhow. After all having a new mooring setup brought out and installed is only around $850.00.

[Bubba]

I would strongly suggest that you have a professional diver move your blocks. All of the ideas above risk damaging equipment, craft, and potentialy get someone hurt.

Yes, the best (and long term economical) way to move the blocks is with lift bags designed for that type of operation. The reason you want a professional to move it is that it can be dangerous.

And for the exercise, the equation that is being used is the correct thinking. And the consideration of "suck" is something that needs to be taken into account.

If you would like, I could do it, or give you a list of names that do this and have experience.

[ApS]

If Mee'n'Mac's numbers are close, you could use a low-tech approach.

Locate an aluminum canoe and secure long 2x8's lengthwise across the thwarts. Shim the seats so as to spread the stress across the length of the canoe.

Make a bridle (or two) out of chain and attach to the mooring block(s).

Fill the canoe completely with water so as to just sink the canoe level with the gunwales. Attach the chains so there's zero slack, then bail out the canoe. Since a canoe can carry (displace) two 250-pound+ passengers with ease, it should be able to lift the concrete blocks.

You should be able to clear the bottom by an inch (or even less) and can move it at will.

Even the best hot-dipped galvanized steel chain gets corroded quickly in Winnipesaukee's waters. At just ten feet of depth, I'd eyeball the chain's condition before you start. Heck, even the concrete takes a beating -- top and bottom.

Having said that, I've restored a 50-year-old concrete mooring with all the metal corroded from it. (And wouldn't feel right abandoning a mooring on the bottom anyway).