Mercury 150 four stroke charging issues

[dunesend2]

New boat to me with a 2017 Merc 150 FS. Previous owner installed [2] new group 24 batteries in October. I charged via an onboard charger overnight to 13.5v. Let sit for a few days, current voltage is 12.0v. Engine starts and runs fine but won't get over that 12v range. Inspected fusible link..blown...replaced with new 100a, still no jump in voltage. Put a multimeter on the alt output lug....no voltage. Replaced the alternator. Again 11.8-12.0 v, engine starts runs fine, run up to 2500rpm to excite the alternator, still maintains the 12v range only. What might I be missing?

 

[leachy]

disconnect the batteries and test the voltage, start the engine and check the battery voltage at the battery terminals. If low id say there is a voltage regulator issue. Thats a big short to blow 100A fuse.