Berkeley 12-JC vs 12-JG

[TyAlley]

I have a question for the jet boat guys! I have a 21’ open bow jet boat with the 12-JC pump in it. I spent all winter building a nasty 550-600 HP big block Chevy for it and it does about 60-65MPH. I understand the 12-JC and 12-JG pump are bolt on swaps and my question is, would it be worth it to bolt on a 12-JG pump with a droop snoop to my 21’ boat? I would like to make it faster and I figured with a droop snoop getting it out of the water more would make a difference.

 

[FSH 210 Sport]

I know very little about Berkeley Jet pumps, but I did a quick search and it appears that the droop snoot is to place the exit of the water jet lower in relationship to the pumps exit point on the transom. If this results in this structure being in the water flow as opposed to being out of the water flow in my mind it would slow the boat down as there will be increased drag.

The question(s) that normally come to mind are; Is your motor reaching the peak rpm’s expected? If rpms are low, over propped, then an impeller with a lower pitch will help raise the rpm’s. If the rpms are too high then you could be underpropped and you would need an impeller with more pitch. This is all highly dependent on the engine you built, are the AFR’s correct so that it is running at a mixture that would create peak hp, is this engine fuel injected with MAP, IAT, ECT and 02 sensors that feed into an ecu that will place fuel delivery into the desired place in the 3D mapping?

Pitching a prop is a regular thing in the marine world to get to rated rpm. On my jet boat for example there was too much pitch for the altitude I am operating at and I was not reaching rated rpm so I had the impellers pitched for my altitude.

Hope that helps,

 

[TyAlley]

I know very little about Berkeley Jet pumps, but I did a quick search and it appears that the droop snoot is to place the exit of the water jet lower in relationship to the pumps exit point on the transom. If this results in this structure being in the water flow as opposed to being out of the water flow in my mind it would slow the boat down as there will be increased drag.

The question(s) that normally come to mind are; Is your motor reaching the peak rpm’s expected? If rpms are low, over propped, then an impeller with a lower pitch will help raise the rpm’s. If the rpms are too high then you could be underpropped and you would need an impeller with more pitch. This is all highly dependent on the engine you built, are the AFR’s correct so that it is running at a mixture that would create peak hp, is this engine fuel injected with MAP, IAT, ECT and 02 sensors that feed into an ecu that will place fuel delivery into the desired place in the 3D mapping?

Pitching a prop is a regular thing in the marine world to get to rated rpm. On my jet boat for example there was too much pitch for the altitude I am operating at and I was not reaching rated rpm so I had the impellers pitched for my altitude.

Hope that helps,

This does not answer my question. Also the droop snoop is meant to lower the snout to raise the boat out of the water creating less drag making it faster. My question is, is it worth it to do it on a 21’ jet boat.