2 Questions- on Batteries and Yamalube 2m

[jdevoid]

I replaced my batteries b/c of low voltage and age two weeks ago.  my voltage went back up to 12.  two weeks later the one deep cycle battery went from 12 to 11.6. The other battery is my starter battery @ 1000.  I have a feeling I have a draw or an in op alternator.
Any simple things to check b/f the more costly solutions?

I have a Yamaha 225 ox66 engine.  The new performance Yamaha 2m oil seems to have an additive eliminating ring stick- says so on the container- SO is Yamaha Ring Free not neede?

[GoneFission]

Check the voltage with the engine running - it should be about 13.5 volts.  You can run a current test, but if you're getting about 13.5 with the engine running, the alternator is working.   Check the cell-to-cell voltage on the deep cycle battery with the engine off - just put the leads from the voltmeter down in the acid to check voltage - each should be about 2 volts - sometimes a new battery will have a weak or defective cell.  Remember deep cycle batteries require a deep cycle charge for optimum charge.  

Hope this helps!