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Hello everyone. I have a problem that I cant seem to get to the bottom of. I have repowered my 1998 2335SS, 5.7 EFI gen+. Bad riser and leaked into the cylinder through the exhaust valves rusting the pistons to the cylinders. New everything except alternator. Serial number OLO12155. I put her in the water two weekends ago and ran up and down the river for a good day of break in. Ran perfect like the new engine it is. I kept everything basically stock. I am running at about 70PSI oil pressure, 170 to 180 temp with a 160 thermostat depending on the load it's under. I only idled it through the no wake zones and back to 2500 through 3800 rpm during the eight hours of running we did. Put it back on the trailer and headed home to wash and flush with fresh tap water. Nothing changed until this weekend. Same thing, put her in the water ran it hard for a while. half way through the day, alarms went off causing it to go into a sort of limp mode? idles fine in neutral and under load until the RPM hits 1800 to 2000. Alarms constant until I limited it to the 1500 RPM range. looked up in my manual (service manual number 24) the diagnostic test for the trouble code 14 "Coolant Sensor Voltage High (cold). I am using the Codemate ECM trouble code tool. As I followed the diagnoses tool and had the 12 code three times and then the 14 code three times back to 12 again. I replaced the Engine Coolant Sensor even though it tested at 2600 ohm range which is normal at outside temperature 80 degrees here today. I also checked the voltage with the key on and had the required 5volts between wires 410 yellow + and wire 814 black -. there are no reason I can find for this code. There are no water blockages pump works well and the oil pressure is great. This is a sensor that controls fuel delivery not the temperature sending unit to the gauge. I consider myself very good with engines and electronics. Auto mechanic for many years before I got my Masters License in electric. I'm not a professional marine mechanic but I understand all the concepts. I don't want to be a part changer so I am asking for advice as to further troubleshoot this issue. I guess the MAP sensor could cause this issue too but the trouble code is specific to the ECS. grounding is good the batteries are brand new and charged. This has to be a sensor causing the ECM to alter fuel delivery. Did I mention it does surge while it is alarm. I checked the Cap rotor and a couple spark plugs and all are in perfect new condition. I could see some misfire and rough idle if it were an issue with the ignition system but not a full alarm and change in fuel delivery. I have also checked the connections to the ECM (EEFI1 or 2 I'm not sure)  and they are clean. I traced the wiring looking for any damage and found none. I really hope its not an ECM issue. The MAP sensor will be my next route.  Thank you in advance for any direction that you can give.

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Thank you for your reply. I don't see where I stated that it is a Bravo 3. Sorry.

Just yesterday I have removed the housing and inspected it for any blockages or build up. While idling the thermostat does open "I also checked it in a pot of water on the stove" I checked the sending unit which works perfectly. The Engine Coolant Sensor and gauge sending unit record water temp from the shared water jacket. I thought of switching the two on the housing to rule out the possibility of obstructions or air pockets at the sensor. Do you think that should be my next troubleshooting task?

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