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Two Versions of the Oberdorfer Pump

Two Versions of the Oberdorfer Pump

How do I tell them apart to determine which gasket I need?

In 2004 Oberdorfer changed the seal on the cover plate from a paper gasket to a reusable "O" ring. The paper gasket included in kit Z2548 will not be used on a pump equipped with an "O" ring seal. If you have a later pump with an "O" ring seal, use our part number Z3645 that includes the impeller and the newer "O" ring. 

This screw between the two ports holds a separate cam inside of the pump. It indicates an early version of the pump with a paper gasket.

Early pumps were machined with traditional mechanical milling machines

The cam was a separate part secured into the chamber with a machine screw

The same time Oberdorfer changed as the gasket, they changed another characteristic that will help you to determine if you have the paper gasket or the "O" ring before you open the pump. Order the proper parts in advance before you need them. Early pumps have a separate cam inside the pump body which flexes the impeller vanes and causes the pump to pump. This cam is secured to the pump body with a small machine screw visable from the outside of the pump.

If your M series Universal engine still has an early pump, order our Engine Spares Kit #Z2553 or our Impeller Kit #Z2548. For other engine models, refer to your respective boat category by starting with Shop by Boat.

Notice in this newer pump the cam is machined as an integral part of the pump body, not a separate part. A flexible impeller pump can pump either direction depending upon the rotation of the impeller, In this photo the pump is rotating clockwise. Inlet is on the right, outlet on the left.

Later pumps were machined with digitally controlled milling machines

A digital machine is programmed to create the cam shape directly from the machined body. No separate cam is required.

With the advent of CNC machining, the cam shape is milled into the pump body in one operation, eliminating the need of a separate part. Digitally controlled milling provided another opportunity: improve the seal by milling a small groove in the pump flange where an O-ring is fitted.

Since both of these changes were made at the same time, from the outside of the pump you can determine if your pump uses a paper gasket or an O-ring.  If your pump was built around 2004, Look for the machine screw head between the two ports. If it has the screw you have a paper gasket. If there is no machine screw you have the "O" ring seal.

If your M Series Universal engine has the later pump with an "O" ring seal, order our Impeller Kit Z3645. For other engine models, refer to your respective boat category by starting with "Shop by Boat".

Notice the cam adjacent to the body of the pump (in the upper right hand corner of the drawing at) This drawing is of the older version of the pump that uses the paper gasket (#3 on the drawing).

What is included in a Catalina Direct impeller kit?

You can't replace the impeller without replacing the gasket too. Even the O-ring should be replaced periodically to guarantee a good seal. Suprisingly, the gasket doesn't automatically come with the impeller from the factory! 

Our kits come with the appropriate seal. Z2548 includes the gasket (#3 in the drawing).  Our kit Z3645 includes an O-ring in lieu of the paper gasket. 

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