Good pump, still no water

[C-worthy]

I have a 1970's 4 hp Mercury outboard with no water coming from the indicator hole in the back of the motor. The impeller is new. When I take the lower unit off, hold it far enough into water and turn the shaft by hand, water rises out of the pump discharge so the pump has to be working.

With the lower unit off, I can blow compressed air (15 psi) into the indicator hole. Air flow seems very restricted. A little air comes out the bottom of the power head somewhere up inside the exhaust housing but no air at all comes out through the copper tube that connects to the water pump. The copper tube itself is not plugged. Here are my questions:

1). Does the pump water normally get split inside the power head with some coming out the indicator and some coming out somewhere else up inside the exhaust housing?

2). Do power head water passages ever get plugged?

3). If so, how do you clean them? Can I fish a small flexible cable like a bicycle brake cable around through the passages?

4). Is the bottom end of the copper tube supposed to fit tightly into the discharge tube of the water pump to send 100% of the water up the tube? Or is the water pump-to-copper tube connection supposed to leak some?

Lots of questions. Thanks for your help!


Brian

 

[C-worthy]

Re: Good pump, still no water

I just answered my first 3 questions. It helped to find the plug marked "FRESH WATER FLUSH".

I still need some help with the 4th question though. Should the copper tube be loose in the water pump discharge or should there be some sort of seal there?

Thanks!

 

[stackz]

Re: Good pump, still no water

you sure the copper tube thing in question isnt just a rotted old thermostat? have you checked to see if the thermostat is frozen closed or open??

do the older engines even have a thermostat?

only reason I ask is because the thermostat in my 90hp engine sure as hell was a weird shape/design to me.

 

[thriller]

Re: Good pump, still no water

I just answered my first 3 questions. It helped to find the plug marked "FRESH WATER FLUSH".

I still need some help with the 4th question though. Should the copper tube be loose in the water pump discharge or should there be some sort of seal there?

Thanks!

What answer did you end up with for the first 3 questions? What is the fresh water flush plug for? It is all new to me.

 

[Motor Boater Bill]

Re: Good pump, still no water

Yes, there should be a seal at the connection from the water pump to the copper tube--it should not leak there.