Where to get replacement o-ring for march pump?
It is skinny silicone oring in the pump head.
http://www.pumpagents.com/MarchPumps/0809-0027-1000.html
That’s for the plastic pump head.
Try these guys: http://www.tescopumps.com/servlet/the-MARCH-MANUFACTURING-cln-Parts/Categories
I used them when I upgraded to the larger impeller.
Edit: now that I have the part#, here’s Tesco’s oring: http://www.tescopumps.com/servlet/the-283/march-oring-viton-te-dsh-7r-dsh-md/Detail
and of course the bigger impeller: http://www.tescopumps.com/servlet/the-226/809-815-march-pump/Detail
Sierra Equipment in Miami had parts for mine. 305-592-0224. I bought a ceramic thrust washer for 7.77, but the shipping was 10.00!
I’ll be that you can measure it and buy several from McMaster Carr for a lot less money.
Do that and I’ll buy some from you. I wouldn’t mind having a spare or 2. 
Interesting. What made you get a larger impeller? Is this specific to the 815, or can it be used on the 809 too?
More beer has the O ring –
March Pump - Replacement Gasket | MoreBeer. They also got me the larger impeller to reduce cavitation and increase flow. The bigger impellers are worth it.
The upgraded impeller will fit March pumps model 809 HS with an operating RPM of 3050 or 3500. It will have this on the data placard. Quoting from another source, the HF impeller increases the max head height from 12.1’ to 18.6’ or from 5.3 psi to 8.01 psi. I believe it and yes it is worth it.
Thank you guys.
More Beer is out is stock so I will try TescoPumps.
Cool, thanks. According to the pump manual with the parts list, it looks like this is the only difference between the 809 and the 815. I’m hoping that this will help with some intermittent cavitation problems I’ve been having.
I forgot that I needed a new thrust washer when I ordered last night so I called up Tesco this morning. They were already packing and threw one in for free instead of trying to reprocess the order. Great service!
What differences have you experienced?
TIA, Tom
The larger impeller provides quick primes, better throttling capability and improved flow when recycling through chillers. Hell, you could probably rig it to pressure wash your deck.
Even if your pump is rigged correctly i.e. below whatever you are pumping out of and inlet down, it just seemed “troublesome” at times to get a flow started. If you have this problem and you’ve done your best to isolate any air leaks, this should help. If you’ve been lucky and never had a flow problem, stay with the smaller impeller. Here’s a pic showing the difference.
I’d be worried about the large hop pellet, leaf, etc.getting close to that large impeller and jamming the pump. I’ve heard mine make some pretty strange noises after dumping some Irish moss into the boil.
bo, it is a magnetic clutch. jamming can’t hurt it.
Works great for me, sounds like you don’t need it.
I know it’s magnetic, but jamming or partial jamming can hurt the impeller and with the closer spacings this can get worse.
Don’t get me wrong, I like the idea of the larger impeller, but it scares me a little.
Why are there leaf hops getting into your pump? 
I tried a filter and that was a disaster, so it’s now an open copper tube. Sure some leaf hops will get through there. For the most part I use pellet hops anyway and they’re sacked.