Mercury 5hp problem

[Merc1]

Hello there,
I was hoping someone could help.
My Mercury 5hp motor wasn’t pumping water at the end of last summer.
Over the winter I changed the impeller, which was completely done.
I filled wheelie bin with water and put the motor in last week and for about 30 seconds a good jet of water came out, then it stopped.
I then took the impeller out and tried it the other way round. This time there was just a dribble of water dripping out.
I thought it might be a problem with the thermostat so I took it off and tested it – it’s working ok.
I then tried the motor without the thermostat fitted and there was a weak jet of water being pushed out.
I would have thought any water being pushed out of the motor would have some force behind it.
Has anyone any thoughts on what the problem might be or if I’m doing something wrong? Any help would be appreciated.
Many thanks

 

[fastjeff]

The vanes of the impeller must be lagging (falling behind) as the shaft turns. You might have parts of the old impeller lodged up there in the power head. If so, it requires power head removal at the very least to clear them out (by back flushing).

Jeff

 

[Merc1]

Thanks Jeff, I'll see if that solves the problem.