Engine gets way overheated

[Spidylou]

Hi I took the boat out for the 1st time yesterday and it seems that the water is not circulating through the cooling system The boat is a 1991 Carteret 17 footer And the engine is a 3 leader mercruiser alpha 140 horsepower Yet the engine cooling system was working just fine last season but does not seem to be circulating this season On the water I took off I mean I disconnected one of the hoe's lines for the cooling system and noticed no water passing through as we ran the engine The cooling system is intake from the Lake water through the engine I'm assuming it could be the impeller but I don't know why it wouldn't be working if it was working just fine last season I'm pretty sure it's not the thermostat because no water was circulating whatsoever.
Any ideas...if so. Would anyone know where I cld get the parts needed too?
Thanl u in advance

 

[Dieter]

If no water is circulating at all start -with the impeller. I had a similar issue ran fine one fall, day after launch in the spring a vane broke off the impeller and completely blocked water flow out of the pump . How long has it been since th impeller was changed.

If the impeller is desinigrated you will have to back flush out all the pieces