The story continues. Took out head and disassembled it. Found nothing wrong. Impeller and other grinding bits and pieces up to spec. However during process flushed out the head. Found that duck weed had almost filled the flush ring and after four days of soaking pressure water still material came out.
Reassembled and reinstalled only to find problem still existed. Out with the snake and you guessed it, it could not be pushed through. After wasting an hour or so and in utter frustration out came the blade and off with pipe. On land using Hugh's pressure still no flow. So I started to really bend and twist the pipe and more high pressure water. Finally water broke through. Lime,toilet paper,duck weed and the metal face of the flapper valve had formed the mass which caused the problem.
No doubt I wasted time and energy, but the disassemble with cleaning were necessary.
I have reinstalled and moved to solid schedule 40 and being unable to find the bits and pieces for 1 1/2 in settled for two. What the hell, it just reduces the friction. On the other hand given that the boat had little or no use for a number of year, buyers beware. I do not know what to do, but heads are a blessing and curse. Bill