stalling at 1016

[farmer brown]

Hey All

Ive been having issues with my fermentation targets. A number of my last brews are starling at around 1016 where Im aiming for at least 1012. Here are a few other details:

1) Mashing at 65-66 (strike 75c)
2) Adding 1tsp yeast Vit per 25 liter
3) Using MaltMiller Ale Yeast 2 (Which i think is Maurubrew 514)
4) Fermenting - 23c (starting at 26)

What Ive noticed is my 200 Liter fermenter is 23c at the top and around 17c at the bottom. What may have been happening is the yeast is dropping and going dormant. stirring sometimes helps but still doesn't ferment down to 1010/1012

Do you think its work getting a little submerged pump to help mix from bottom to top?

Another thing thats at the back of my mind is water treatment? I use around 1ml AMS per liter of water and around .4g DWB per kg malt for my pale ale. The guys at Murphy and Son were happy with my calculations for London Water but can over-cranking AMS or DWB affect the fermentation?

Is there anything else that can stall fermentation?

I've just ordered some US-05 to see how that goes, if that stalls then I definitely have a problem!

Thanks All

 

[brewtim]

What's the pitching rate?
What's the OG?
What's the expected attenuation of the yeast?
What's the size of the batch?
:wha:

 

[farmer brown]

What's the pitching rate: 80g for 160 liter
What's the OG? 1042
What's the expected attenuation of the yeast? This strain rapidly attenuates fermentable sugars with typical wort falling from a gravity of 1040-1045 resulting in a beer of less than 1008.
What's the size of the batch? 160 liter

Here is a bit of info on the yeast:

Mauribrew Ale 514 Yeast
This strain was selected based on its ability to produce English-style ales. It is a strong fermenting strain with rapid attenuation of fermentable sugars. Most noteworthy is this strains alcohol tolerance, producing commercial ales with up to 9.5% alcohol.

TYPE
Saccharomyces cerevisiae
Top Fermenting Ale Brewing Yeast

TEMPERATURE RANGE:
Thanks to its high temperature tolerance Mauribrew Ale can ferment from 15°C up to 32°C.
Desirable flavour characters result with this strain through the 16-24°C temperature range.Beer structure may benefit from fermentations with this strain after acclimatising to lower temperatures for prolonged yeast contact at 12-15°C.

INOCULATION RATE : 50-80g/hl

RATE OF FERMENTATION
A rapid fermenter at warm ambient temperatures, resulting in a typical fermentation time of between 3 and 7 days.

DEGREE OF ATTENUATION
This strain rapidly attenuates fermentable sugars with typical wort falling from a gravity of 1040-1045 resulting in a beer of less than 1008.

ALCOHOL TOLERANCE
This ale yeast is renowned for its tolerance in commercial beer styles with up to 9.5% alcohol.

YEAST HEAD FORMATION
Though a top fermenter, this yeast produces nominal yeast head through stages of maximum gravity loss.

FINAL CLARITY
One of the selection criteria used for this strain was its generally very good settling properties even at warmer ambient temperatures 20-30°C.
12.5g pack