1965 40 HP Water Pumping Question

[elark7]

I have used my small boat very little this summer. The last time out I noticed a strange pumping problem. When idling and up to mid throttle, I have normal water flow from my 40 horse. When I go beyond mid throttle the stream starts to wane then completely dissappears at full throttle. I pulled the lower unit and checked the impeller and it still looks and feels new, was replaced last March. I removed the thermostat and this had no effect on flow. Just wondering if it is possible to have a blocked passage somewhere in the head? Any thoughts on how to check without a complete teardown? Thanks.

elark

 

[Joe Reeves]

Re: 1965 40 HP Water Pumping Question

Thermostat is important, replace it! Regardless of how the impeller looked, install a complete water pump assembly. Think about it.... if there was a blockage, would the water be flowing thru it at mid throttle?

 

[wulf311]

Re: 1965 40 HP Water Pumping Question

Did you check the impeller housing when you had it apart. Those old one had a habit of pitting the housing.

 

[elark7]

Re: 1965 40 HP Water Pumping Question

The housing and plate were replaced with the impeller. They were still as new, smooth and shiney. I have put maybe 15 hours on the motor this summer. I even checked to see if the slot was worm where the woodruff key lines up the impeller to the shaft. Could the impeller be slipping at high rpm's even though it does not appear to be worn at the key locator? Could the key be worn ?, it is the only piece that I did not replace.