Not charging?

[crazyjoe]

I switched motors on my 2006 Tracker from a 2006 60 hp Merc to a 1996 75 hp. The tach works fine but,the charging gauge shows minus when I run the boat and I have to charge the battery after ever 2 times I run the boat? any suggestions?

 

[Andrebass]

Something wired incorrectly?

 

[jerry shack]

I switched motors on my 2006 Tracker from a 2006 60 hp Merc to a 1996 75 hp. The tach works fine but,the charging gauge shows minus when I run the boat and I have to charge the battery after ever 2 times I run the boat? any suggestions?

does both wiring harness's on the motors have a 8 pin black wiring harness connector?