A “Wet End” is the collection of parts which come into contact with the liquid.
A “Pump Less Motor Kit” is all the parts except the motor. The “Wet End” is a subgroup of the “Pump Less Motor Kit”.
A trim is when the impeller diameter is reduced from its standard full size.
Magnetic Drive Pumps are trimmed for two major reasons.
First, a trim allows a pump to become closer to the targeted duty point of the application. An oversized pump will have to be restricted with a valve to meet the desired duty point, and it will consume excess horsepower, wasting money.
Second, magnetic drive pumps are restricted by the horsepower of the motor and the strength of the magnets. Liquids with higher specific gravities and viscosities require more horsepower and magnetic strength. If the motor is overloaded, it will burn up. If the magnets are overloaded, the magnets will temporarily lose their connection to each other, resulting in the impeller ceasing from turning, and as a consequence, liquid will not leave the pump. The magnets will not reconnect until both magnets come to a complete stop. Trimming the impeller reduces the flow, head, horsepower, and NPSHa, so it prevents the motor and magnets from becoming overloaded.
Carbon Bushings and Marine Pumps
Running dry is when the impeller of a pump is rotating without any lubrication.
March Pumps are designed for the impeller to spin around the impeller shaft with lubrication. Without lubrication, the impeller will hit the impeller shaft and start producing heat. If the pump housings or impeller are made from plastic, the heat will over time surpass the melting temperature of the plastic, and the plastic will melt. When the plastic melts, the plastic parts will either seize onto each other, causing the impeller to become immobile, or a hole will form allowing the liquid to leave the pump and possibly damage the drive magnet or motor.
- Ensure all filters and strainers are not clogged.
- Have a carbon bushing installed into the impeller.
Carbon dissipates the heat much better then plastic. Using a carbon bushing, it will take a longer period of time for the pump to suffer damage if it is run dry. Furthermore, if the pump is being run dry, the pump will make a louder screeching noise, which can be used as an informal alarm that there is a situation with the pump.
If the pump is already purchased or installed on the boat, it is still possible to utilize a carbon bushing. A new impeller, one calling for the carbon bushing, can be ordered and installed by any user into their pump. Changing the impeller does not violate the warranty.
If I use a carbon bushing and the pump stills suffer damage from running dry, is the pump covered by warranty?
The pump will not be covered under warranty, for any pump, even with a carbon bushing, given enough time, will suffer damage if it is run dry. Installing a carbon bushing does not make the pump impervious to running dry, it only provides a degree of protection.