Mercruiser 170 charging system

[Newguy1330]

I'm having some issues with a boat that was just purchased. Got it from a friend and everything was fine when we took it out and ran it. The next day I went out and noticed that he left the battery switch on and the boat had no power as the batteries were dead. Went to put a jumper box on the 1 battery and unfortunately the cables were put on reversed. Switched them over and got the boat to start up. After about 15 min it turned off and had no power. Got it running again and it stayed on so we took it out only to have it loss power again and had it towed in.

Took both batteries out and had them charged at autozone to find out 1 battery was bad (the one that we hooked up the jumper box wrong) purchased a new battery and installed them back in. Started the boat up and ran it for an hr at the dock no issues Turned the battery switch off and placed a battery maintainer on 1 battery.

Came back today, which is a few days after and started the boat up. It ran for 5 minutes and died again. No power. What is going on?

 

[alldodge]

Need to break out a voltmeter and start with the battery and work your way around.

If the motor will not turn over check from the key to the starter solenoid.

If the motor will turn over but not start, check to see if you have 12V at the coil.

 

[Newguy1330]

Today it ran great for 5 min then I lost all power. When I put a jumper box on the battery it turns over

 

[alldodge]

Start by removing the battery cables at both ends. Check the ends to make sure the cables are not corroding inside. Use sand paper or other to clean the ends up to shinny metal.

Then pull the 10 pin engine connector off and check/clean the corrosion.

Start the motor and check at the battery that your getting close to 14V

 

[Faztbullet]

Get ready to replace rectifier...$$$$$

 

[shaw520]

Get ready to replace rectifier...$$$$$

yup,.... 170's have a history for that.