Mechanical vs Electric Water Pump


Which water pump should I run for my application?  Mechanical or electric?  The question has been asked thousands of times and depending on who you ask, the answer could be inherently different.  Each one has their pros and cons and in order to make an informed decision it is probably more prudent to understand what you’re trying to accomplish and then weigh the pros and cons of each.


Are you battling an overheating issue?  Is your vehicle predominantly used on the street or on the strip?  Are you looking for more horsepower?  All common questions along with a host of others so let’s start breaking it down and weighing things out.



A mechanical water pump is just as it sounds, mechanical.  It pulls coolant from the radiator and distributes it to the block via a belt drive connected to a shaft that turns an impeller to create flow.  Not all mechanical pumps are created equal in terms of flow and rotation but for all intents and purposes they are broadly considered the same in application.  The important thing to note is that as RPM increases, so does flow.



An electric water pump functions similar to a mechanical pump by pulling coolant from the radiator and distributing to the block but does so via an electric motor that spins a shaft connected to an impeller.  And just like their mechanical counterparts, not all are created the same, but share the similarity that they are all run electronically.  Other than being powered by electricity vs a belt one other fundamental difference from their belt driven cousins is that rather than being variable flow coinciding with engine RPM, electric pumps are a constant flow.



More often than not a mechanical water pump will be the choice that most people make because it covers all of their needs.  They flow better at higher RPM, perform better in traffic and are much easier to plumb for things like heat and AC. 


However, the biggest drawback to a mechanical pump is that it is mechanically driven by the engine.  Usually used in conjunction with a mechanical fan this pairing robs the engine of precious horsepower if ponies are what you value.  So for someone who is performance driven and looking to squeeze every last morsel of power out of their engine then going the electric route is certainly a good option.   



Comparing mechanical water pumps can be somewhat difficult as a lot of manufacturers don’t publish flow rates because flow is directly proportional to pulley ratio and this can vary widely.  They are generally going to be offered in a cast iron or cast aluminum housing and a cast aluminum housing will help dissipate heat much quicker as well as tipping the scales to the lighter side by a few pounds.


Looking at electric pumps there are a lot of different variations in the market but the most common are the two-leg style as we call them and most of them will flow at 35GPM.  There are a few manufacturers that manufacture electric pumps that have a different shape or design and some with a higher flow rating upwards of 55GPM.  For most applications a 35GPM pump is going to suffice.  However if you want more than that and your wallet will take it, the 55GPM pumps are some of the best out there



A few things to keep in mind when looking at mechanical pumps are going to be whether the pump you need is standard (clockwise or CW) or reverse (counter-clockwise or CCW) rotation.  Hub Height is also important to know as a lot of vehicles had what they considered to be a long and short.  Hub height is usually measured from where the water pump mates to the block or timing cover, to the outside edge of the flange or hub that the water pump pulley bolts to.  Pilot shaft is important to note because there can be different shaft diameters in both factory styles and in aftermarket offerings.


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