Ericson 29 head problem

I recently bought an Ericson 29. My head is clogged or not flushing properly. The head has an eletric flush. No holding tank. I need a detailed diagram for the system, or advice on what to do to fix this problem. I have tried plunging the head, adding vegetable oil to lube things up. The through hull discharge valve is open. The intake valve works properly and slowly fills the head with water. Anyone with advice please help. I have hit a wall with things to try. I would rather fix this problem myself than taking it in to someone to work on the head.

Mariner's Honey :esad:
 
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