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1
Engine Mechanical / Electrical / Tach reading high - where to start troubleshooting?
« on: March 20, 2018, 09:49:20 AM »
My tach is reading incorrectly, based on the high RPMs that I'm seeing that don't line up with the impeller and horsepower curve.  My tach is showing 4800 RPM at full throttle but I'm running a heritage AA impeller with a 325HP BBC. 

So, where do I start?  Re-wiring?  Replace the tach? 

2
Jet Pumps / Berkeley Pump - need help
« on: February 27, 2018, 03:50:56 PM »
Alright guys, I need some help here. 

454BBC (passenger/2 bolt/ ~325HP). 
Berkeley JC pump. 

WOT - 4900 RPM & 46 MPH - Sea level with 4 adults
WOT - 5100 RPM & 50.6MPH - 3700' elevation - 1 adult.

Pulling a skier, the pump cavitates and doesn't produce much torque. 

Based on the above the assumption has been that the impeller was a C cut, which was causing the high RPMs and cavitation from a stop under load.  I was getting ready to send the pump out to get rebuilt with a new impeller so I pulled it apart and this is what I found inside.  A2 cut impeller, what looks to me like clean leading edges, no obvious issues.  So what gives?  Why are my RPMs so high and having trouble with the holeshot?   

Now I have no clue what to do with the pump rebuild.  I'm glad I might save some money on not needing a new impeller, but at a loss for performance issues. 

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