2000 90 hp Johnson: power loss above 2400 rpm

My 2000 90 hp Johnson overheated while running at around 4000 rpm for 30 minutes. I believe the overheating was caused by a large sheet of plastic that snagged on the fin at the bottom of the motor, restricting water to the impeller. After removing the plastic from the motor, the red warning light on the dash went off after about a minute. Now however, any time I run above about 2400 rpm, the engine runs very rough and provides no additional power. Below 2400 rpm, it seems fine. I limped back to the dock at 2300 rpm, running for about 20 minutes. Any ideas what causes this? Could I have done permanent damage by continuing to run the motor instead of waiting for a tow? I removed the prop, and there is nothing tangled around it. Beyond that, I have very little knowlege about what I should do next.<br /><br />Thanks in advance for your help and advice.

Re: 2000 90 hp Johnson: power loss above 2400 rpm

If that piece of plastic starved the impeller of water at those rpms,it likely damaged the impeller, and the waterpump will need to be replaced.I recommend you perform a compression test on the engine and insure that no cylinder scoring occured as a result of the overheat.Otherwise the engine may be going into the s.l.o.w. mode and keeping it from performing above the 2400 rpm level as a result of the waterpump damage that may have occured.This s.l.o.w. initiation however should sound an overtemp alarm or overtemp light in conjuntion with limiting the rpms to 2500.The s.l.o.w. system will not prevent engine damage due to an overheat ,but rather reduce the possibility of more extensive damage by reducing the rpms that the engine can be operated at.