Because everybody needs a pump The sharper among you will note that the pump is round. Indeed, this is by design. The square-bottomed pumps are convenient for sticking in square spaces, but are inconvenient it you want to rotate the pump a few degrees for clearance on the outlet or some other reason. Outside diameter is 55mm, height is 24mm not counting motor nor height of the allen screw heads. Impeller diameter is 35mm. Another view of the DC pump. The motor mount plate on this pump is designed for a brushed 550-size motor. More significantly, look at the mount plate. You can rotate the top to any facing that you wish, allowing you to point the motor wires in different directions if this helps fit the pump in the boat better. The pump will go together with 4-40 allen-head screws, and will also fit M3 screws if desired. I like M3 better, but upon further reflection, most of my older gear is 4-40 compatible, and my friend Brian's QE, a very near sister ship, will be running 4-40 hardware. Below, you can see the pump disassembled. On the left, the motor mount plate (upside-down), and on the right, the pump body. Note that they have a circumferential lip for proper alignment and a better seal. The other neat part about this design is that you get quick access to the impeller. Removing the 4 main screws, you separate the mount plate fromt he pump body,a nd the impeller is instantly visible for troubleshooting, if necessary. No having to fiddle with a setscrew through a tiny weep hole in the pump body to pull the impeller out of the pump body! (If having to do that hasn't annoyed you in the past, sorry. It has bugged the crap out of me). Previous iterations of my home made pumps have had larger-than-usual pump outlets, which are great for more flow, but not very standard. So this one has a standard sized pump outlet, same size as BC and Swampy (I haven't played with a Strike pump yet; if they're the same as Swampy's were, then mine is same as theirs) pumps. Below, you can see the impeller, a fairly typical 4-blade impeller, also printed in ABS, with a brass 1/8" collar chemically welded into the center to give positive lock on the motor shaft. The impeller also gets a gentle acetone bath to strengthen and smooth the blade surfaces. The little dingus hanging off the motor mount plate (top edge) is flash from printing. I will be posting more next weekend as Brian K and I do flowrate testing Haven't made any for selling (yet) but they'll likely go for $20 each, with a piece of hose and a 1-unit restrictor. I will be making a different motor mount plate to fit the 28mm-class brushless motors, and also a smaller 1/2-unit DC pump. **DC is Damage Control, not the motor type Navy talk, eh, wot?!