I wouldn't be so quick to dismiss the "unusual bump" as a detriment. Instead of assuming it disturbs flow in a negative way, consider what that bump does from a hydrodynamic point of view.
With it rising at the centerline of the shaft, it creates low pressure on the backside pulling flow around and up the backside of the shaft. Think of it kind of like a spoon at the front of an intake. If it were smooth like a Berk, flow would hit the shaft, split around it and create low pressure on the backside of the shaft. I can see that creating cavitation far more than the bump would. Just an alternative consideration.....
This is a concept that I hadn't considered. If you will bare with me over the next few posts, I would really like to explore this further.
I am not trying to thread jack, I am gain a better understanding myself.
As long as the OP doesn't mind, I will post here. Otherwise I will move to a new thread.
This is why we dismissed some of the AT suction housings to fishing boat status: Approaching this from a cylinder head flow perspective; we feel that the greatest non-turbulent mass flowing suction housing, that doesn't overcharge the pump, and with even pressure across the face of the impeller must be the most efficient.
Looking at the AT and Dominator suction housings, that bump is really not there for flow purposes. It is there because these suction housings, compared to a Berkeley, resemble a raised port cylinder head intake port. The bump is there to maintain wall thickness around the thrust bearing and packings.
Typically the suction housing is drilled near the top and bottom of the impeller inlet eye. These pressure ports are monitored by pressure transducers connected to a data logging system. Keel pressure (vacuum) and bowl pressure are also monitored along with speed, RPM, etc. All of these could be graphed together to observe trends.
One such trend is that when a Berkeley suction housing cracks and is switched to a Dominator housing, the lower impeller inlet eye pressure drops. Chris @ B1racing blended his with epoxy on 418 and the the lower suction pressure increased, resembling that of a Berkeley housing. As the epoxy is now long gone, the pressure is back to typical Dominator pressures.
On boats where a fishing boat suction is swapped for a Dominator, pressure increases. Being that Dominator is AT's top dog pump, and that bump has been mostly removed, I would think that if it was a flow device rather than an ease of manufacturing and tooling concerns, it would intentionally be exaggerated in the Dominator housing.
To be continued...
