Suzuki DF30 power loss

[Frank Acampora]

I have a 2003 four stroke Suzuki DF30. The engine starts right up, idles very well, but for the first 5 minutes or so It will not develop full power. It can not get the boat to plane. Then, as if something chicks in, she goes to full power, will push the boat to 30 MPH, and runs at top speed from then on. It is getting fuel and is cooling well--new fuel filter and new water pump impeller.

Any suggestions on what to check? I am leaning toward a bad temperature sensor or bad dashpot. There is a signal lamp on the center front lower cowl that stays on while running.

Thanks in advance