Mercury 150 Won’t Start

I have an Encore250 with a Mercury 150. I went to start it this season and I put the key in, turned to on and everything normal happened with the one loud beep, tach going to 7 then back down, fuel pump kicked on, and battery read 12.6V. When I turned key to start, I heard a click then it all started over with the loud beep, fuel pump kicked on, tach went to 7 and back down, etc. That kept happening. When the key is on, the tilt motor just hums and won’t work. With the key off, the tilt motor works fine. Also, I unplugged the auxiliary cables from the battery to test just the cables to the motor and nothing at all happens at that point. I took off the cowling and top cover and see that the starter will shoot up when I try to start it but then nothing. It hasn’t turned over once. It’s like it wants to start but quickly looses amperage. I cl3aned the connections at the battery and even tried a different battery, both fully charged, and same issue. I juggled the throttle to make sure it is in neutral and still nothing. It worked last season and I did the 300 hour maintenance on it a week ago but didn’t check to see if it would start before or after. Any ideas?

Sure sounds like a battery issue to me. Do the cables get hot? Can you turn the engine over by hand(not sure if you can grab the flywheel on there or not, maybe use a screwdriver on one of the teeth and make sure it turns). My concern is that a cylinder froze up over winter.

I might try removing the plugs and see if it will turn without compression.

Found the issue later that day. All made sense when I realized I had to have aux negative connected for anything to happen and the starter wasn’t getting enough amperage to turn over. A mouse or something chewed through the negative wire connecting the battery to the motor!

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