water flow problem

[eric.101]

I have a 04 yamaha hpdi that sat for a while and is not getting water flow through motor. I tried flushing it through the garden hose attachment and it wont go through, I cleaned out the tell tale tube it was blocked up but still wont flow through. I dropped the lower unit and hooked garden hose to the copper pipe and it would flow through the tell tell but still can't flush through flush attachment. I swapped the lower unit with another one that was working on a diferent motor and it would only dribble out the tell tale and motor overheated. What can I do to fix this? Is there a chemical I can pump into flush valve to free up blockage? Any help would be appreciated. THANKS

[boats.net]

Might check the hose that is on the flusher to make sure it's not kinked under apron, when connect water hose to copper pipe see if water comes out flusher ok.

[eric.101]

No water came out of flusher.Hose was not kinked or clogged.

[boats.net]

Must have blockage, possible in flush hose.