3 h.p.outboard. Limited drive. Throttle on and motor revs without increasing drive or speed. Drive key? How fix?

Yes that is a tranny issue or finale drive as they call it.

What Colorado do you have ? 2 wheel or 4 wheel drive ? Sport ,sport LS 3.5L , Z71, Z71 LS. etc. what size engine ? an does it have electronic throttle control ? I have factory service info an it is not showing that code .
DTC P0506

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
DTC P0507

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0507 Idle Speed High
Cleaning the throttle body mite take care of it !
Cleaning Cleaning An Electronic Throttle Body Safely

There are videos all over YouTube that cover this subject quite nicely.
winterizing an outboard motor YouTube

Have the vehicle checked for DTC'S - diagnostic trouble codes ! Do you know what electronic throttle control is ? The gas pedal assembly has electrical connector an sensors inside ,hooked to the PCM / ECM - engine computer . The engine computer uses these position sensors inputs to control the DC motor on the throttle body to open the throttle plate to control the speed . Plus there are position sensors inside the throttle body to input PCM/ECM to see if it's calculations are corect . Your best bet maybe to take it to a qualified repair shop .
Drive by Wire Function and diagnostics by Wells

Reduced Engine Power Mode
When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
• Acceleration limiting--The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
• Limited throttle mode--The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
• Throttle default mode--The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
• Forced idle mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
- Ignore accelerator pedal input.
• Engine shutdown mode--The control module will disable fuel and de-energize the throttle actuator.

No it wont overheat !!! Change the solinoides over on the trimand see if you can raise engine and now not lower ! if yes then replace solinoide !

can not reverse in the morning wen it is coll have to give speed for 30sce. and also for drive

If the throttle cable is not attached properly to the throttle body or you have a bad motor mount, the throttle cable may be pulling the throttle open as you shift into gear. Open the hood, find the throttle cable on the throttle body. Inspect how it is connected and also how the cable is fastened in the engine comoartnent. Next, watch what happens as someone else starts the truck and puts it into gear. If the engine shifts significantly, check for broken motor mounts. If the throttle cable is misbehaving, correct the installation.

Make sure that the ****** isn't slipping.

it would not be an O2 sensor, period, they would never cause a high idle, have u had this checked for trouble codes? A sticking idle speed control air bypass can cause this problem as well as a throttle position sensor, but run the codes, Kragen does it for free was well as other parts stores.

the inside of the prop has a rubber between the prop itself and the inside splines to act as a shock absorber,say if you were to hit a rock. that rubber had spun out and the splines are turning inside the prop. the prop is screwed. seen it 100 times before.