T&T: water pump problems

[ed]

My new to me boat was pumping fresh water OK until yesterday. Now I can't 
get flow, nothing was changed. The problem is on the input side of the 
system. It's not an airlock, I took off the filler caps to the tanks and 
that didn't help. Plus it's both tanks. I put in a rebuild kit (sureflow 
3.3gpm) and the suction improved but still no water flow. I think it's an 
airleak around the manifold. The system has an accumulator tank and I don't 
know much about them. Is there a troubleshooting resource I can read?
Thanks

Ed K