pump won't prime?

[Ptownkid]

Been having trouble with water flow to the engine on a 351. When we first start up, we get no flow at all from the outlet of the raw water pump. If I fill the outlet hose with water and then start the boat, water will flow. If I then shove that hose onto the Tstat the water will continue to flow, cool the engine and all is fine. The impeller is good and I can't find any leaks...ideas?

[Jetlink]

What is the overall condition of your hoses?

[Ptownkid]

What is the overall condition of your hoses?

Generally good I think...my first thought was air leak too.

[DAFF]

Try putting the intake hose in a pail close to the pump and start the boat. I bet it pulls water great. Somewhere there is a small fracture in the suction side of the system causing you all the grief. Replace the hose with new and install new gear clamps too.

[wotan2525]

The pumps have a wear plate in them that needs to be replaced/rebuilt. I can't tell you if that's your problem, but you can see my thread about trying to figure it out....

https://forum.supraboats.com/showthread.php?11370-Water-pump-won-t-prime!

[Ptownkid]

I found that thread minutes later...food for thought. The hoses are all 4 years old and in basically mint condition. My main hunch is still small airleak somewhere, but the boat has not done it again since the other day and I've been out a bunch...