pops1:
Scarab Jet:
OK guys, this might sound like an obvious question but here it goes:
Let's assume we have the same boat with the same jet pump and the same impeller. Now, if we were to compare a 350 vs. a 502 motor in this boat and run each of them at let's say 4500 RPM, would both of them go just as fast at that RPM? ( or for that matter at any given RPM?
Thanx in advance...You must make a assumption based on your write up that both impellers are the same cut.
That is whare the two motors will fall apart- ON Torque! The small block is a lighter weight but that is all. The big block may even make the same HP but it make Torque at a lower RPM. To off set this, you are be forced to cut the impeller-Which shortens the duration of water ride (a critical producer). Also on the smaller impeller you cut the vane away (smaller) which causes the bowl pressure to become the offset for the lower thrust comming off the impeller. You now have a larger exit port opening on the smaller impeller(flushing) with a lower thrust entering into the bowl. You also now have reduced your frontal draft by flushing the water out the back (and so on). Torque is the answer or gear reduction to develop comp torque to run the biggest impeller possable at the highest RPM.
What you have developed to offset the torque to HP is design in slippage which is non-functional loss -Dave wink
I know there is some really good information there , I'm just having a hard time following. Pictures w/ clearances would help in this case.