1999 dt150 shift problem

I mounted the motor on the boat with brand new controls. When I shift into forward or reverse the gears grind into place. The motor is idling at 1100 rpms. Is the idle speed the problem or something else.

you need to adjust the shift cables

If you're grinding both ways you might want to change the gear oil, supposing the **** cable is set right. Usually they grind either FWD or REV not both. Old gear oil can cause shifting problems and wear on the internal parts of the lower unit. 1100 is a bit high, 1000 or 950 would be better. Your idle adjustment is a switch on the black box, it should be labeled "IDLE". It manipulates the timing. If you mess with the carbs there is a throttle position sensor that will have to be recalibrated. Some engines (especially larger ones) like to take up the slack toward FWD when you adjust the shift cable. Not a lot, just a little. Make quicker shifts too and avoid grinding the gears if you can help it. You're not really grinding gears you're grinding the clutch dog and they do not tolerate much wear.