This is the only way I know how to explain it but...
Yes it is possible to overpower the pump out of the hole. This is why a lot of people with small impeller cuts run inducers...to keep from blowin' the pump dry out of the hole. On the hole shot the pump has no dynamic pressure in the intake (i.e. pressure obtained by forward movement of the boat and changes with the boats forward speed) to help load the impeller and the engine. A smaller impeller cut won't bite as hard on the hole shot as a larger one will. Because of these factors, a smaller impeller cut can't load as hard as a larger cut impeller out of the hole. Too small of a cut won't be able to provide a sufficient enough load on the engine out of the hole, which allows the engine to spin up too quickly, which blows the eye of the impeller dry, causing the pump to slip out of the hole. Some even run a launch controller on the holeshot to give the pump a chance to hook up without overpowering it.
The whole purpose of a loader is to keep the top of the impeller loaded at speed and help to increase dynamic pressure at the intake. Because of this a loader will increase midrange pull bigtime...but if the loader blocks the intake too much you will sacrifice some holeshot. The main thing is if the eye of the impeller cavitates, you will lose holeshot bigtime.
Here's a great article I found...was written by bp on Hot Boat...explaining what exactly goes on in a pump on the holeshot.
"when an engine is flatfooted off idle, from a dead stop, a significant amount of flow through the pump begins. without the boat being up to speed, restoration of the water to the suction piece is solely based on atmospheric pressure. during those first 2-3 seconds, suction pressure at eye of the vanes on the suction side of the impeller becomes very low, to some negative pressure value (how low the pressure goes is affected by a couple of variables - how much hp is being applied? what is the condition of the pump? what nozzle insert is installed? how heavy is the boat weight/drag effect on acceleration - a heavier boat won't achieve the same speed as a lighter boat; speed increases intake loading velocity, counteracting the low pressure).
pressure at the eye of the impeller can become so low that liquid changes to vapor, causing some degree of cavitation, which negatively affects thrust.
a "cavitation reducer" is a small, mini impeller that is mounted on the shaft, on the suction side of the impeller. the purpose is to increase pressure at the eye of the impeller, to prevent pressure from dropping so low that a change in phase can occur, thus preventing cavitation - consequently it's named cavitation reducer.
a cavitation reducer -might- help you, but then again it might not add what you could be looking for. mine was installed when i had a little over 400hp, and i could tell the difference in acceleration right away. in a heavier layup, with a good tight pump, it can be very helpful in preventing cavitation at the hit. but it's not a cure-all, and needs to be evaluated thoroughly with the rest of the hardware. i've seen guys change impellers, make 1 or 2 laps at the most, jerk it out saying they didn't gain anything. i've seen guys do the same thing with a cavitation reducer. 1 or 2 laps is not sufficient time to gather enough data to make an informed decision, one way or the other. i've seen enough to know they do what they're intended to do, and recently we installed one in my 23' hallett jet along with some other things.."
