Hi,
I bought a maserator pump at West Marine. I was somewhat surprised at how much less a Marine maserator is than a RV one. I think it was less than $100. It came with a 1-1/2" inlet and outlet. I was able to convert to a 1" ID clear tubing, then used several sections of 3/4" PVC tubing to make it to the outhouse that I was parked near. I guess I was using 3 each 5' PVC sections and about 50' of clear tubing.
3/4" garden hose is much smaller, and about 1/2 the free open space of the 3/4" PVC. It took about 10 minutes to drain my 40 gallon black water tank.
Good luck with your project!
Fred.