j hydraulic dredge pump manual

Raw water pump impeller wings face wrong way?

Initial Question

The user attempted to replace their raw water pump impeller and observed that the impeller wings appeared to be facing the wrong way, as if the impeller turns counterclockwise, despite expecting it to turn clockwise based on the water input and output.

JamesG161's Response

The impeller's appearance is correct for a flex vane pump.

Further Discussion

The pump works by transferring water from input to output over the long arc. Sometimes the blades are backwards because when the engine stops it may go backwards half a rotation or so, so there is nothing to worry about.

Maine Sail's Post

Even if you put an impeller in with the vanes completely backwards of the pumps rotation it would correct itself with the first bump of the starter. It is 100% urban myth/dock talk that impeller vanes need to be installed in the direction of rotation.

Additional Observations

Broken screws and pink metal are not great signs for the life of the pump. The color of the bronze is pink, which is a bad sign as it indicates the zinc in the bronze is leaching out. Without zinc the bronze becomes very soft and brittle, likely part of the reason the 2 bolts sheared. It may be time to replace the pump.