I have a pair of 2006 250's on my boat. One runs great no issues the other has 2 problems.
#1. Motor will sometimes not start, turn the key and no ignition. I have replaced the stater, solenoid, and key ignition.
most of the time it will start when it's cold but after running and getting used if I stop for any time and turn the motor off it will not start, nothing, the fuel pump does purge. I leave the key in the on position and use a screwdriver to jump he solenoid and starts right up.
#2. Same motor when running anything above 3900rpm's after about 30 seconds it will start to loose rpm's pull the throttle back below 3900 and will pick back up and run smooth?
Model # E250DCXSDR
Serial # 05132807
1. If nothing happens when the key is first turned to ON then START, a tech will have to use a meter to trace where the voltage is not getting through.
2. I can only guess but it is likely there is a fuel delivery or aerated fuel problem that will not allow full flow to the injectors. Fuel pressure readings at all speeds at both the lift pump and high pressure pump should narrow down the possibilities. A vacuum test of the boat's fuel system and using clear line to monitor for air bubbles is also recommended.
Because there is no gauge or start indication with the key turned to ON or START, go to the source. Check the battery with a load test, remove and clean terminals - no wing nuts, lockwashers and hex nuts (stainless steel) only, then check at engine and the fuse. Trace both ground and B+ circuits up through key switch and beyond.
Obtain a factory service manual for the colored electrical diagram of the engine.
The gauges do come on when I turn the key and I hear the fuel pump run for about 5 seconds, the motor will just not turn over and start, remove the cover and jump the solenoid out and starts.
Test the neutral switch in the control box. Sometimes it may be out of adjustment and wiggling the cotrol handle works.
I have even bypassed the switch, not the cause either.
You will then have to trace the voltage from the battery, through the key switch, and back to the appropriate pin on the EMM. Also check for a consistant 12V on the solenoid primary and a continuous return wire at the correct EMM pin.
It will take a trained tech or obtain a factory service manual, wiring diagram, and follow the troubleshooting guides.
Your dealer is best equipped to handle this diagnosis.