spdfreak

I am having a bit of trouble with one 2003 Speedster 160 with the Mercury M2 jet drive. I was out on my second outing with the boat (bought it used in the fall) and halfway through our day of boating the boat started to beep, one constant beep and the boat seemed to go into limp mode. Long story short is we narrowed it down to the battery. I've since charged the battery and had it load checked and it passed with flying colors! Now my attention is on the alternator. My question is: What should I measure for voltage at the battery with the unit idleing? My initial testing shows 12.5 VDC (measured at the battery terminals) with the boat off. Running at idle the measured voltage is 12.2 VDC. with no movement either up or down. What should one read? My background is typically automotive so my thinking is I should read around 14 VDC. With any luck someone one here can let me know what the right value is so I can avoid a trip to the dealer.
Thanks
S