OG is not matching calculations from pre-boil Gravity

[LilLostCoveBrewer]

So this weekend we were brewing up an IPA. I do all grain with a 5 gallon cooler, 30 qt aluminum pot, turkey fryer. After putting all my ingredients and numbers into beer smith, the software said I'd end up with with an OG of 1.063.

So come brew day, with 12 lbs of grain being used, I have to split my batch sparge into two 2 gallon sparges to fit it all into our cooler. After I collected all the wort (about 6.5-6.7 gallons worth) I got a pre boil reading of 1.046 on the hydrometer. Using brewers friend calculators, that gave me 73% efficiency. Which was exactly what the goal was. Therefore after the 60 min boil, I should hit the desired OG.

After the boiling and chilling, we got 4.8 gallons of wort, so we got a bit more boil off than expected but that should mean a slightly more alcoholic beer. However, after taking the OG reading it only read 1.057? (after accounting for calibrations). How can we be 6 points off? Especially when we boiled more off than expected?

Is my hydrometer just not working properly? I don't understand. I used multiple calculators on the web and they all say that it should read at 1.062-64. What is the deal?

 

[oceanic_brew]

At what temp were you taking your hydrometer readings?

Even when I apply the necessary temp corrections I'm way off. I'm waiting until I get a refractometer to begin dialing in my efficiencies again.

 

[oceanic_brew]

Also you said 6.5 gallons of pre-boil. Is this accurately measured. I assume so but had to ask.

 

[LilLostCoveBrewer]

At what temp were you taking your hydrometer readings?

Even when I apply the necessary temp corrections I'm way off. I'm waiting until I get a refractometer to begin dialing in my efficiencies again.

I took my pre gravity test at 60 and my OG at 68. All numbers were gotten after adjusting for temp corrections and hydrometer calibration.

 

[McKnuckle]

Given 6.5 gallons starting and 4.8 gal post-boil with a 1.057 OG, that indicates 1.042 pre-boil. It was probably a stirring/stratification issue. The sugars are rarely evenly distributed in the pre-boil wort. It takes some effort and time to stir and gather a representative sample. Four points of error is not surprising.

 

[LilLostCoveBrewer]

Given 6.5 gallons starting and 4.8 gal post-boil with a 1.057 OG, that indicates 1.042 pre-boil. It was probably a stirring/stratification issue. The sugars are rarely evenly distributed in the pre-boil wort. It takes some effort and time to stir and gather a representative sample. Four points of error is not surprising.

We didn't stir the wort before boiling so I guess that could be it, however we did collect by using the some hose like a straw and placing your thumb over the top end. That should have gotten a sample through each of the potential layers of sugars and its been the way we've been doing it all along with no issues and all numbers coming out right give or take 1 or 2 points, not 4-6.