3.0L Mercruiser dies

I have a 1999 Bayliner with 3.0L Mercruiser. I recently had it tuned up and a new carburetor top put on. It starts, idles and runs geat but will die after 10 - 45 minuets of running for no reason. It is as if the ignition is just turned off, like the safety switch lanyard is tripped (which it isn't). I try to start it again and it will crank but not start. After 1 - 2 hours of lettting it sit, it will start up again and run fine for another 10 - 45 minuets before dieing.

I believe this is an electrical issue, due to the way it just dies - no sputtering like a gas issue - and it starts and runs fine again after a period of time. I also believe it might be either the electronic ignition module or the coil, because it runs great until it heats up (which is indicative of electronic component heat failure).

I would like to get some feedback from others who may have experieced such an issue or can offer some advice before I start replacing components and hopeing it fixes the problem.

Your comments are appreciated.

Re: 3.0L Mercruiser dies

Just for starts and to make sure we are working on the correct engine, Is your engine serial number 1A072812 or higher

Re: 3.0L Mercruiser dies

The engine S/N is OL087705. It is titled as a 1999 but I believe it was manufactured in 1998.

Re: 3.0L Mercruiser dies

billmcp80 said:

The engine S/N is OL087705. It is titled as a 1999 but I believe it was manufactured in 1998.

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Your right and the correct serial number will help, otherwise we may start looking at the 99 model. I see you have the EST ignition systems. Need to get it to happen again and then determine if your getting spark, which sounds like your probably not. Have a volt meter with you if there is no spark and find the purple wire on the remote start relay (slave relay) and see if you have 12volts. If so pull the plug off the coil and see if 12 volts is there on the purple wire pin. Will it die the same way if sitting on the trailer?

Re: 3.0L Mercruiser dies

Thanks for the reply AllDodge. Is the purple wire you are referring to the one on the connector below the coil?

Re: 3.0L Mercruiser dies

Yes, but for clarity all purple wires are turned on by the key switch turning to run (12V). I knew the coil wire would need to be removed to test so wanted to see if you got 12V another source prior to pulling it.

Re: 3.0L Mercruiser dies

billmcp80 said:

I try to start it again and it will crank but not start. After 1 - 2 hours of lettting it sit, it will start up again and run fine for another 10 - 45 minuets before dieing.

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If you suspect the ignition module or coil are dying due to heat, cool them down with ice to see if either react to being cooled down. Hold a couple ice cubes on the side of the coil until it's cooled and try to start the engine. Then, hold a couple ice cubes under the distributor's base (aluminum plate) until it and the module sitting on top of it are cooled, and see if the engine starts.

I would test the wiring and electrical system as AD suggested, to see if you have power going to the ignition when this happens.

Re: 3.0L Mercruiser dies

Thanks for the reply fishrdan. I will purchase some cold spray and try that on the distrubutor base.