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But I would still check everything with a multmeter too make sure you're getting 14volts out of the alternator and batts when running. I think mine are popping the breaker because all the batts are not fully charged, you might also want to take the battery cables off and set your multimeter to ohms and connect to the cables to see if there is draw somewhere. Ohms should be at least 100, if you're showing 0 there's definately a draw thats running your batteries down and tripping that breaker. ?????Hey mike1960, I live right in Swansea Ma down the river (Taunton) from you. I too have the same problem happening on my port side 318. I think i left the boat sitting on the mooring for to long and the inverter ran the 3 batteries down. When I used it after two weeks, the engine breaker poped and the volt meter went down to around 11.5. I checked batts and alternator with my multimeter and batts showed low 12.6 when running. had the alternator rebuilt cause it showed the same as helm volt meter, 11.5. put rebiult alt. back in and still 11.5. Just by chance I pushed the 25A breaker and the engine went down in rpms, hooked up volt meter and it showed 14.2 @ alternator !!! I then ran out for a 1 hr run to charge the batts. showing 14v on the volt meter @ helm. Coming back I put on the Nav lights and it went down to around 12v and poped the same breaker again. I then disconnected the third battery that I have dedicated to the inverter (which was unhooked all day) and it ran @ around 13.5 all the way home and didn't pop the breaker. I'm goin' to try takin' all batts out and charge them, then re-install and see if all is well if not I must have a draw somewhere, which is another ball of wax. Sorry so long winded, but I think these on line forums help alot, besides I can't complain to the wife, she has no idea what the heck i'm talkin' about !!