1964 Merc 650, #1670xxx. It has been sitting for several years, so I changed the impeller, yet I have no water thru the tell tale hole when running on the hose. The water jackets on the engine are cold and the impeller flush plug shoots water when opened, so I know it is pumping water. Is it possible I am not flowing enough water with a hose to run the tell-tale? I looked up in the casing when I had the lower unit off, and it seems to need a really high water level in order to flow thru it. The passage is clear. Any ideas?
I confused the exhaust post (middle of the back of the engine) with the water tell tale hole (left side of engine, right under water jacket). I could only see a dribble at home on the hose. I had it out on its maiden voyage at the lake on Saturday, and with more volume, it cleared up and flowed pretty well.