Trying to get info on converting 10pin harness to 14pin harness. Looking to upgrade to Merc 525’s that have the 14pin harness. My boat side has the 10pin harness. Do I just need the AGI boxes to convert the digital signal to analogue so my gauges work? Or is there more it than just installing AGI boxes? TIA

There are 14 pin to 10 pin harness adapters available and yes the AGI boxes will convert the signal. Here is a link to the adapter.

https://www.greatlakesskipper.com/me...-10-pin-14-pin

You can get away with installing sending units for the gauges that do not work. We did this on early 2000s power play, it was a lot cheaper than AGI boxes