How to figure boat lift capacity?

thormx11

Petty Officer 1st Class
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Mar 28, 2012
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I am looking at buying a floating lift for my boat. I have found one but the guy doesn't know much about it. I am trying to figure out if the lift will lift my boat. There are 2 round fiberglass tanks. They are 2' wide and 16' long. I have tried to google it but couldn't come up with much for a boat lift.
 

thormx11

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Mar 28, 2012
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I would believe so too, but I am not so much worried about the brand as I am with the lifting capacity. I have done some math with a formula I found online and came up with a little over 6,000 pounds lifting capacity, not counting the weight of the lift subtracted. I looked on hydro-hoists website and they advertise a lift with the same size tanks as a 4,000 pound lift. Not sure if they add in any extra weight for a safety when calculating lifting capacity?

I think my boat has a dry weight of about 2900 pounds. It has a fuel capacity of 76 gallons, which should weigh a little under 500 pounds. If you add a couple of people, gear, etc. I would say I would be getting close to 4000 pounds.
 

harringtondav

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May 26, 2018
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I just did some calcs. Not accounting for tank wall thickness and the radiused tank ends, those tanks would displace about 6300# of water. So I think your 6000# estimate is good. Good enough for your 4000# load. And a couple more people, and beer, and.....

BTW, your 76 gallon fuel tank sounds more than a little large for a 2900# boat. Maybe take your boat to a scale to verify before you plunge in.
 
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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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my 26' boat has a 75 gallon tank and weighs 3600# not sure I would put a boat that long and that hung that far over a hydro-lift on each end up in the air. while it would hold it if your CG is centered, it would top over if its not.
 

thormx11

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Mar 28, 2012
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I do not know the exact weight, the only estimate I can find is from nadaguides specs. Not sure if they are even close to actual weight?

The boat is a 1995 Century Arabian 240. Its actually 23.5' long, but it is a fairly deep/wide boat. I know it is a 76 gallon tank, I checked the plate on the top of the tank.
 

harringtondav

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thormx11 Again, to be sure take your boat, trailer and tow vehicle to a scale and get a weight. Then weigh the tow vehicle separately. The difference is the boat and trailer's weight. The trailer's weight is normally on a decal on the trailer. For a 2900# boat, I doubt your trailer weighs more than 1000-1200#.
 

garbageguy

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May 8, 2012
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Doing some rough calcs is pretty easy - requires a simplified force diagram (I need a sketch when doing this stuff anyway). What is the lift's support based on, displaced water? Air pressure contained in bladder(s)? Metal structure?
 

thormx11

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Mar 28, 2012
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I do plan to take the boat to the scales, I have a Pilot truck stop 7 miles down the road from me. Problem is, I have a lot of the boat stripped down redoing a few things and getting ready for paint this winter, so it wouldn't be very accurate right now. The trailer is an aluminum tandem axle I beam trailer (Continental Brand). There is no plate on the trailer though, The boat/trailer was wrecked while going down the interstate and the trailer had to have quite a bit of work done to it and it was probably removed then.

I am going down tomorrow to take a look at the lift, I believe it will be big enough. If not, then I guess I will have a boat lift for sale in the spring :p
 
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