So im working on an 03'Tige with a 350 MAG MPI Tow Sport package. Merc. The thing is my Diacom USB software won't connect when i have his ign on key on but it will work when the boat is runing, possibly low battery? gonna charge it but wanted to start my thread first. Second Problem is when im running it after about 10min it just shuts off and the ECM kicks me out and then i can't connect again or start the boat like it might be in guardian mode but can't check to see because like i said the ECM won't let me link. i have no codes when its running and everything looks ok but the water PSI from the pump is only at 1.97PSI @ an Idle. help please.
also thinking maybe a bad ECM

You're providing a very broad description. It's tough for people to just start throwing out guesses without knowing more or being there to hear it and watch it. Does it die or shut off abruptly or stutter? Is it losing fuel, spark, run rough before dieing???

Otherwise, just guessing causes someone to start at the fuel tank and go forwards which is a heck of a lot of typing etc.. Do some troubleshooting and come back. Hopefully you can get somewhere.
The water pressure is pretty much normal for idle on hose with medium to low water pressure. Just bump the throttle a hair and the pressure will come up and cool the system better while you're running it on the hose.

Seemingly if you had a bad battery wouldn't it fail to start for 10 minutes?

Depending on which version you have, they all will kick you out when engine dies. 2.1.0 or older will not automatcially re-connect. 2.1.8 does.

You say there are no codes but does it give any type of error message upon connecting or just before disconnnect?

yea i thought the same about the battery but i know that if the battery voltage is low the ECM won't function, because at first i did the ign on key on ya know an wanted to check an see if it had any codes in the memory. it just dies like it loses spark thought an that made me think guardian mode but then when i try to ign on key on if won't connect to the ECM from my diacom software. sorry for the vague descriptions im only 21