Mercruiser Power Issues - Electrical

[mashoo]

[FONT=&quot]Hello,[/FONT]
[FONT=&quot]I have a 2002 Bayliner Trophy Boat with a Mercruiser 5.0L Alpha MPI. We are having issues with it dying on us why we are out. It will run for a bit then the engine will stop like we turned off the key, it will restart but only for a min if that. This happens over and over. I measured the volts on the batteries and they are good when the engine is off but when the engine is running it drops randomly to 4-5 volts. I am thinking there is a short of some kind that only happens when the engine is running. Maybe bad alternator?[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]We have had lots of work done over the last year so many things are new or replaced but the electrical side of things is still mostly original. [/FONT]
[FONT=&quot]Where should I start?[/FONT]

 

[makomark]

If the computer doesn't have a solid +12VDC supply, the engine will do as you have described...
I'd be inclined to change the main relay first and ensure ALL of the battery cable CONNECTIONS ae clean and tight...

 

[mashoo]

<p>

If the computer doesn't have a solid +12VDC supply, the engine will do as you have described... I'd be inclined to change the main relay first and ensure ALL of the battery cable CONNECTIONS ae clean and tight...

Thanks makomark, Im not sure if my engine has a computer. It is fuel injected but im not familear with a computer on it. Engine is a 2002 Mercruiser 0M344267. I do have the service book 31 for this engine.</p>

 

[mashoo]

Just to close this out for future readers, our alternator was bad. I took it to a shop where they tested it and then took it apart and tested each part. They found it worked properly when cold but after it warmed up it would intermentily stop working. A new alternator fixed the problem.