Where are your trim and tabs at, those numbers sound like everything is down, what is the elevation where you boat?

Those #s are with the drives all the way out and then brought in just enough to optimize MPH. With the drives in, RPM is around 4000.

Elevation here is about 500'

Something has to be wrong, do you have gill exhaust, if so have you checked for reversion?

No, stock exhausts, etc. Engines are OK (they can pull the 24s right up to the rev limiter). Don't know why the RPMs are so low with the 28s.

:confused:

Anyway, I'll try a pair of 26s.

Isn't Gil stock on the 500's?

Yes, that is why I asked about the reversion,because gill exhaust have had reversion issues on the 500's, the cmi's are the answer

liquid asset,

Which CMIs? The standard elbow top ones? Thanks.

Mecury went to the elbow tops