Seems that my water pump is having a problem pulling from the fresh water tank. It works well if I use the winterization valve and pull water in from a bucket of water, but slows to a trickle if I switch the valve back to the tank.
I've tested the pump in isolation and it seems to work just fine.
When I pull the cap off of the intake side of the pump (circled in red above) to clean the filter out, I was surprised that there wasn't a flow of water coming from the the fresh water tank. Possible that this indicates an issue upstream of the pump?