I'm updating this thread just in case someone else has the same problem one day.
I've purchased a new water
pump kit. I took the lower unit off and checked the impeller. Everything look new and in perfect condition. I lubed and reassembled everything and started the engine in a baril of water. Same amount of water was coming out (little stream on neutral, a few drops in gear).
I took the lower unit off again. Cleaned the pee hole with a pipe cleaner. Then I put a rag over the water intake tube(the one that links to the water
pump) and blew compressed air (computer cleaning canister but a compressor would do the same thing) in the pee hole. A beige fibrous debris flew out, the size of a garbanzo bean. It could be algea.
I've reassembled everything and tested the engine. It is running fine now.
Don't you like happy endings?
Tx for everyone's help.
Yves