5.3 ls volvo penta pump performance suggestions/information with AB impeller

Hey,

Ive been testing a 5.3 ls style engine in a 19 foot scarab with a pjx volvo penta pump and a AB impeller. The boat does really well but i need more thrust. It is a stock 5.3 and claims to make 379 lb-ft at 4300 rpms and 344 hp at 5100 rpms. So i just put in a AB impeller upgraded from a C. Since i have more surface area on the impeller vanes should i not bore the nozzle to match? Ive been researching mixed flow pump optimization and cant find much material does anyone have any good books are good tech articles on mixed flow pump performance/theory?

Thank you all for your time this is all new to me and i have no idea where to start researching these topics.

I just wanna go fast

nathan

 

Are you planning of boring both the intake and outlet?

 

It would be just the exit nozzle.

 

Without the jet manufacturer's key to impellers you are left with guesses. The s.c. Volvo pjx jet was developed by "Legend jets" if I recall correctly. The identification system ("A", "AB" etc) is unique for each manufacturer.

Here a few examples for 350 hp:

Berkeley @ 4550 rpm: impeller A2;
@ 5100 rpm: B;
@ 5750 rpm: D;

Dominator @ 4250 AA;
@ 5100 C
@ 5700 E;



Together with the nozzle, the impeller is determining the operating point for the pump, where the engine power input is exactly balanced by the pump power. You have no chance to get it right "by chance".

You have probably gone from an impeller that was close to optimum for your rig to one that suits an engine with maximum power at lower rpms. This means that your engine will not produce max power with the AB impeller. Depending on the pump characteristics, you may, or may not get a rpm increase when opening the nozzle.

With bigger nozzle, you will increase the flow, which in turn means that you are closer to the cavitation limit during acceleration, but you will probably lose top speed as well. So, without correct info on impeller characteristics, your matching procedure is a guesswork.

In order to come up with any relevant advise, we need to know more about your jet, most important is impeller inlet eye diameter, shaft diameter and exit nozzle dia or shape. In addition, what boat speed and what rpms have you achieved, and with what equipment.