Impeller Didn't Push Water

Last week I replaced the impeller and gasket between the base plate and impeller housing on my 1999 40 HP Force. Afterwards I thought my water pump issue was fixed because my motor would spray water wonderfully. I'm using muffs on the lower intake vents fed by a water hose.

Today, I replaced the thermostat. I started the motor and no water came out. I turned the water on a little more in case it needed more water flow coming into the bottom intakes and checked the muffs position over the intakes. Nothing. Then the overheat buzzer went off, so I shut off the motor.

I removed the thermostat housing and the the thermostat was fully open, but it was pretty dry in there. So, I pulled the lower unit off and checked the impeller. Nothing looked wrong. The impeller fins are turned into the housing the correct direction given that the drive shaft turns clockwise and I don't have any damage to the impeller, the base plate or the housing. So, I reinstalled everthing to check it again. Water flow again was excellent.

Why would I have great water flow one week and nothing the next?

Re: Impeller Didn't Push Water

The hose? How much pressure do you have??
You say you turned it up?? You should always use it full force.The pump will use what it needs.You can't over pressure it.
Try putting it in a big bucket.
It needs to be in deep.At least 2-4 inches over the cavitation plate.

Re: Impeller Didn't Push Water

Clues point to the thermostat and its installation and/or muff performance.

Re: Impeller Didn't Push Water

Well, I have used an old trash can before, but it's always worked with the muffs, too. If I'm just checking for function and not working on the motor then I use the muffs. Water pressure was good, but I turned it up anyway. Same water faucet setting when it did work. If I turned up the faucet all the way I would probably blow off the muffs as I have very good pressure at the house. Thermostat is in correctly and functioning well. If it happens again today or the next time I run it, I will let you know. It's a head-scratcher. Thanks guys.

Re: Impeller Didn't Push Water

It's a mystery. Impeller did fine today. I'll watch it to see what happens from now on.