Quote Originally Posted by "G" View Post
Not reccomended by the battery manufacturer or the engine manufacturer ? Is it because the alternator on the four stroke outboard is not designed to charge a lithium battery ?

I could see a problem with a lithium's bms shutting down the battery when alternator fully charges battery to it's cut off voltage. This essentially disconnects battery from the motor. A lot of motors need the battery to run, even if that battery is fully charged. That interrupt may cause running issue. You can also read online that lithium starting batteries can be hard on alternators. It seems people are running lithium starting batteries with out issues, so more time will tell.