I've not had a lot of experience with oil exchange pumps myself so my advice may be of limited help, but I have used a Reverso pump system on the Swans that I've run in the past. http://reversopumps.com/products.htm
These pumps have also given me some trouble but I believe primarily due to the fact that the retro fit installation was a little poor. It is really important to install the pump as low down as possible, below the level of the engine sumps to enable the pumps to prime easily. Regardless of whether or not they say they are self priming, moving the pump lower in the bilge in my case made a huge difference. If the pump runs dry for a long time whilst priming, the rubber impeller will suffer and quickly fail, moving the pump below the sump level will minimize the length of time to prime the pump. Also to assist the prime, you should heat the oil up before draining to lower the viscosity. Run the engine for 5-10 mins, no need to bring it up to running temperature but just a little warm to aid the flow.
Sorry I can't recommend a number of other pumps as I just don't have the experience of anything other than Reverso, but the above suggestions made a big difference for me.
Best of luck
Captain Ian Fagg
James D. Stearns | Boat: Sas Jaz | 02/07/2011
The following links to the one I have used for 5 years on 3 engines with good success. It was recommended by a lifelong shrimp boat captain.