[Chris Burkard]

Stop!!! If you are overloading the engines, you could do irreparable damage to the engines.

Your engines are rated to turn 3000 RPM under a full load. For safety, it is best to let them overturn about 50 RPM when fully loaded (100% Fuel, 100% Water, 4 people and gear) as this allows you to have a dirty bottom or dirty fuel and still fall within the safe range (3050 RPM). Light load, you should be turning 3100 to 3150 RPM.

At 2700 RPM light load, you have something wrong!

1) Make sure your bottom is clean!
2) Make sure your shafts turn freely when the engines are off and the transmissions are in neutral. You should be able to turn them by hand via the propeller.
3) Make sure your fuel is clean and fuel filters are clean.
4) Have engines checked (injectors?, turbos? fuel pumps?).
5) Props? The original props were likely 23"x29" - 3 Blade Federals with #7 Cup
6) If everything above is in order, as mentioned above, photo tach the engines for exact RPM. Gauges are notorious for being 50 to 100 RPM off. I've never seen gauges 300 plus RPM off, but I suppose it is possible. I would photo tach them under load (be careful!) it can be very dangerous to photo tach the engines while underway. You may want to hire a mechanic to do this for safety reasons.
7) If you truly are at 2700 RPM under load (everything above is good), I would pull the props first and verify the diameter, pitch and cup are close to factory settings. If they are, then you need to move to the engines.
8) If the above is all good and you are at 2700 RPM, then I would say you have a power problem, either worn cylinders and rings, bad turbos, bad fuel pumps, bad injectors or a combination.

I'm hoping it is something simple, but you need to figure it out before any damage is done.