Marinette Boat Forum

Changing Raw Water Pump Impellers
This is a tough job on 'twins', and it's even tougher if you put the pump housing in backwards. (Ah-hem!) The impeller has to 'screw into the housing' in one direction as well. The below photo and diagram show how the parts go, but a smart mechanic marks the parts before taking them apart. (Ah-hem!) The impeller shown had at least three years running on it and was still good. Best to change them BEFORE they start throwing blades. If yours is chewed up, be sure to backflush the oil cooler, to remove the impeller pieces--or else the new one will be destroyed. (Thanks to Norm for the second photo below.)

Question / observation....
On the port impeller - rotation of the impeller's shaft would be clockwise? If so, would not the bend of the vanes go in the opposite direction than shown? The action of the vanes should "pull" water up through the inlet and then out thru the outlet as they're compressed against the impeller body "offset" (wrong term probably... mea cupa...).

Likewise for the starboard engine. Being reverse rotation, it would go counter-clockwise. The vanes would then bend opposite to what's shown, pulling water up thru the impeller's housing and out the outlet?

The view in the sketch is looking forward. The vanes bend back, lagging, as the rotor turns.

The trick here is to MARK the housing BEFORE you remove the pump so the inlet/ outlet is in the right orientation.

Jeff

I think I should change mine this year. Is there a gasket that goes between the pump housing and bearing housing? I want to make sure I have everything before beginning the process.

Thanks!

If you buy the Sierra kit, the different gaskets are included. I just bought one last week. I think there were two different o rings and two to three flat gaskets.

I change mine annually and keep the old one as a spare. Its cheap insurance.

Eric

The problem with the Sherwood pumps is the required maintenance that is NOT performed on most of them.
Sherwood: 4 years major rebuild kit Cost: 188.00
Sherwood: 2 years minor kit Cost: 80.00

Impeller: Every year
I just replaced both mine. The bearings no grease left lots of corrosion .

dave

Thank you ericinga!