Offshoreonly.com - Mercruiser 6.2 MX alarm help

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Simple to rule out or rule the ECM 555 itself for being the alone problem - keep in mind he has twins.

Warning - do not swap over the known good ECM from the good running engine with NO ALARMS to the bad running engine. Why because you know its still good and do not what it possibly knocked out.

Important - You take the SUSPECT or POSSIBLE bad ECM from the bad running engine and install that correctly on the good running engine to SEE what happens. Keep the known good ECM in a dry safe place until after the testing to reinstall it back on the good running engine.

Another warning, before touching the ECM's UNHOOK all battery power however per your app, then only apply battery power after all ECM connections are connected to start that engine..

Next I wear a static guard wrist band when I am working with ECM's and PCM's. Especially with new ECM's / PCM's because Merc will not warranty them from electrostatic discharge damage. Merc and the rest OEM marine manu's warn you very heavily against electrostatic discharge shock from persons handling the ECM's meaning that even static discharge can harm the ECM / PCM just by touching them. FYI

Thanks for all the advice guys. Since I don't have smartcraft gauges, does my engine still have a water pressure sensor as referenced by Nate?

You will need to post your engine serial numbers and I am asking do you have the 6.2 MX Black Scorpion engines ? I did not notice until know your posting of the MX model.

Everything goes by engine serial number not year model.
With that said just because one person has an engine does not mean yours is the same set up so again engine serial numbers are very important.

I am surprise on Nate's boat that it was hard to find a bad water pressure sensor and or low water pressure because that all you have to do is run the boat on the water with the scan tool hooked up then monitor the water pressure parameters of the PSI from the water pressure output on the scan tool. If low or high or very out spec ranges will pin point the problem area. Not hard at all. A simple test to say the least.

I don't know if they're the Black Scorpions or not but I will get the serial numbers to you asap. They definitely say MX on them though.