Macerator plumbing

[SV Alfresco]

I completely revamped my head plumbing a couple of years ago. New head, tank, hoses, vent filter, and macerator.  The problem I'm having is it takes a long time for the macerator to prime. The location is near the top of the tank. I thought maybe I should lower it but didn't want it filled with crap all the time. Last year, I was winterizing the tank with the boat out of the water and ran the macerator (with a bucket underneath the boat) and it primed right away. Same thing this year. I'm wondering if there is not enough push with the outlet under water creating an air lock. I'm going to replace the impeller as a first try.  Anyone have any thoughts on a solution?

Mike

[S/V Deo Volente]

I think replacing the impeller will fix it. The resistance of the underwater discharge won't bother a working pump. Theoretically you could have an air leak on the suction side, but you would probably notice that.