My friend has the boat purchased 2 new batteries however upon using them it was running rough on the one. Looking at his gauge and even under power the 1 shows 12v. While not going over 12 sounds to me like a bad battery not taking a charge. Thinking for a minute it seemed odd under mild throttle and cruising 2500 rpm it didn't have had enough power to fire the plugs properly. There was no radio on or load besides the motor and gauges. It can use either battery or both and using the 2nd battery or both settings run fine and shows 14 volt. It last had a tune-up including plugs I believe 2 years ago. He uses the ethanol free at his Marina and told me used the proper sta-bil. We're going to swap out the battery and probably run spray some carb cleaner into it in a couple days. Is there anything else to check such as would plugs need changed this soon?
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