I have a 496HO and recently changed my impeller.
The old impeller was missing one blade.

When I'm running the boat it will not run up to full speed and when I pull the stick back down from running full throttle to idle the HO goes into limp mode (Gaurdian mode) for 10 to 30 seconds. I am also having trouble keeping it running at idle. I put fresh fuel in and replaced the fuel filter but still no luck. I'm sure it must be the new impeller. I searched the site for anwsers but no one seems to have had the same problem.

Anyone got any ideas of whats going on?

Thanks for your help
Ron

try back flushing the system find the missing glade its messing with your water pressure

The motor was running fine even with 1 blade missing on the impeller.

So whats the best (easiest) way to back flush the 496ho system

i had a similar problem,,,it was the water pressure sending unit,,,,some are at the raw water pump,,,and some are on the power steering cooler,,,replace the idle air control valve to fix the idle problem,,,