impeller dragging?

[41magnum]

we replaced the ancient, brittle, chipped impeller in a 35 Merc that's 35 yrs old...….. and the new one drags slightly,
is that normal?
It tinkles out the back fairly well, but at higher rpm's it fades some.

I posted this last fall some time but can't find it and forgot bout it...

 

[wrench 3]

If you put the new impeller back into the pump housing you know how tight a fit it is. It's going to have some drag. What did you lubricate it with?

 

[gm280]

There is a reason for it fading (some) at higher speeds. The impeller actually makes two different types of pumps. At lower speed (RPMs) it is a displacement type pump. If you remember when you installed the impeller, It installed off center to the pump body. That makes the displacement pump. As the speed (RPMs) gets higher, it becomes a centrifugal type pump. As the speed increases, the impeller blades act more to sling the water to the outer side of the pump body from centrifugal action. Just a little info from my Johnson's Shop manual...

 

[Mohawkmtrs]

Go boating...and find something else to worry about.