In this article, we’ll explain how to identify your Jacuzzi Magnum’s Impeller and Diffuser as a Type A or Type B revision. In addition, identifying which style of diffuser you own will ensure you get your pump up and running as quickly as possible.

The Magnum pump has been manufactured under several brand names, like Jacuzzi, Carvin, and Cantar. The pump model name has also been fancied up a few times with the additions of Plus, Force, Force 3, and all other iterations, but the general design has stayed the same, for the most part.

Picking out the correct part style for your Magnum can be a minefield of serial numbers, model numbers, and manufacturer dates. But we’ll show you a few tips and tricks to make sure you find the right parts for your pump.

Pump Model Number

First, let’s confirm that you have a Jacuzzi Magnum. The Magnum’s model numbers have gone through little changes over the years, but the general format is easily deciphered.

Let’s break it down so that we can figure out what you have:

1UMF-S
1 = Horsepower
UMF = Uprated Magnum Force, Service Factor 1.25 or less
S = Dual Voltage, 115/230 volts

Now let’s try a more difficult one:

2MF-S2
2 = Horsepower
MF – Full Rated Magnum Force, Service Factor of 1.3 or higher
S2 = 230 volts only

Check for the Diffuser Fin

The quickest way to determine if you need the A or B style is to open the pump and view the diffuser. Type A has a distinctive fin on its diffuser, whereas Type B looks like a more traditional diffuser version.

Check the Impeller & Diffuser for Part Numbers

Most parts of your pool pump should be labeled or stamped with a part number. As you can see in the below picture, the diffuser has a very noticeable part number, but this could wear off with age. Impellers are more likely to have the part number stamped into the front or back plate of the impeller.

Finding the Correct Impeller

With all the information we have gathered up until this point, like the model number, age of the pump, and diffuser style, figuring out the correct impeller should be simple.

The information that ensures a good match is the impeller part number. This number is usually stamped or written on either the face or backside of the impeller disk, as shown in the picture.

If the impeller part number is missing, the next best thing is to match using measurements. Most Magnum diffusers and impellers have been carefully measured and noted on dimension images.

Two other key features to note when comparing impeller dimensions are the number of vanes and the width of the impeller plate. First, count the number of vanes through the front face opening of the impeller. The vanes are like the props of an impeller. They create the vortex to create the pulling force.

For some horsepower sizes, the only differences between the ‘A’ or ‘B’ style are these two points. In the figure, we illustrate how to take the width measurement. First, measure the width, including the front and backplate and the vane holes.

Replace the Complete Pump’s Drivetrain

If you want to avoid opening the pump but still need to replace the diffuser and impeller, the best option would be to replace the pump’s drivetrain. The Jacuzzi Magnum would include the impeller, diffuser, and seal housing. The seal housing is this barrel drum piece that holds the seal plate and is the base for the diffuser.

This is the best way to identify your seal housing via a parts manual:

“The front of the seal housing is slightly different in each version there is a raised section around the front where the impeller sits, about 1/4″ tall. There is a 1/4″ x 5/16″ notch on the outside edge. This raised section extends all the way to the outside screw holes on 2 of these and does not extend all the way to the outside on 3 of these. On these 3, the raised section drops down by about 1/8″ at 1/4″ from the outside holes. Measuring the inside diameter of the raised section and noting whether or not the raised section extends to the outside holes is the only way to identify each type raised section specs: 5064-18 inside diameter: 4-9/16″; does not extend to the outside edge 5064-18a inside diameter: 4-29/32″; does not extend to the outside edge 5064-18b inside diameter: 5-3/16″; does not extend to the outside edge 5064-18c inside diameter: 4-7/8″; extends to the outside edge 5064-18d inside diameter: 5-1/4”; extends to the outside edge markings: “Patent pending 9982″ may be molded on the motor side.”

I suggest purchasing the updated ‘B’ style because these are likely to stay in production longer than the older ‘A’ style.

You will have to purchase replacement housing for pumps manufactured in 2003 and before to line up with the updated models. If this is the case for your pump, you might want to consider replacing the whole pump.