Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

[Jerry Wagner]

Please help me out if you can with an 18" Sea Ray... My 1996 3.0LX Mercruiser started blowing my ingnition fuse when the boat was under power (appx. 5 minutes later). After it heats up, it will continue to blow new fuses immediately as soon as you replace the fuse and turn the key one position to your right to energize the gauges. It will blow fuses until the motor cools, and then the fuse will remain intact and start up fine. It will not get hot enough during idle to ever blow a fuse. Some say it is a bad coil. No parts store one around here can test a coil under a load. The internet sources say the resistance of primary to secondary windings on a coil should be between 10000-15000 ohms. Mine reads 8000 cold when the boat will start fine without the fuse blowing. I tried heating the motor up to purposely blow a fuse and then take readings off my coil. When the fuse blew, I immediately took coil readings. The coil still reads 8000 between windings. I also tried reading from both primary and secondary windings to ground. Both readings show infinite resistance. I do not suspect the coil as being the source of ground, but I may be missing something. Thanks!!!

 

[tommays]

Re: Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

if you ohm the wire supplying the ingition circut to ground (-)and try it again when the fuse blows i would think you have a dead short some were when the motor is hot <br /><br />if you have a wireing diagram it will show were the wire goes more places than you would think the books deliverd with the boat have a good diagram in them my 1995 boat came with the engine and outdrive install manuals<br /><br />tommays

 

[chefmikey]

Re: Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

Sounds like a short, maybe to a sending unit oil or temp. Start tracing, hop some wires, you will find it. Just think, you could be tracing wires underneath the dash of a 2004 Luxury vehicle, I guess that is the bright side..... Good Luck

 

[Bondo]

Re: Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

A Dead Short Should be quite Easy to find......<br />Just start taking smaller systems out of the circuit, Till you find the Bad 1....... <br />

Just think, you could be tracing wires underneath the dash of a 2004 Luxury vehicle

I think I'd rather be sent to NoWhere Afganistan, <br />In Shorts,+ Sandals.. With a canteen Full of Salt Water... In July.....<br />Than to Do That........

 

[Jerry Wagner]

Re: Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

Well, Thanks for the help. I forgot to post the results, but luckily for me the short stayed present even after the motor cooled down. I work in electronics, so it was not hard to find at this point. After disconnecting gauges and accesories one at a time to isolate the cause of the ground, I found that one of the wiring harnesses was sitting directly on top of the block. Heat had melted the electrical tape and melted through two purple wires. I still cannot figure out why it only seemed to happen when the motor was hot. Vibrations seem like the more likely candidate. A shorted wire to groud is a short regaurdless of temp. Perhaps just a coincidence and when the motor was running wide open the vibrations casued those purple wires to short. I have seen stranger things either way. Now if I can get this cutout switch / shifter / cable problem fixed I might have some fun before the end of the summer. Thanks again!<br />J. WAGS

 

[Jerry Wagner]

Re: Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

Well, Thanks for the help. I forgot to post the results, but luckily for me the short stayed present even after the motor cooled down. I work in electronics, so it was not hard to find at this point. After disconnecting gauges and accesories one at a time to isolate the cause of the ground, I found that one of the wiring harnesses was sitting directly on top of the block. Heat had melted the electrical tape and melted through two purple wires. I still cannot figure out why it only seemed to happen when the motor was hot. Vibrations seem like the more likely candidate. A shorted wire to groud is a short regaurdless of temp. Perhaps just a coincidence and when the motor was running wide open the vibrations casued those purple wires to short. I have seen stranger things either way. Now if I can get this cutout switch / shifter / cable problem fixed I might have some fun before the end of the summer. Thanks again!<br />J. WAGS

 

[KaGee]

Re: Mercruiser 3.0 blows fuse/stalls (Is everyone stumped?)

Is what they make wire loom for! <br /><br />I have loomed all of my harness that has any chance of coming in contact with something potentially hot or moving. <br /> <br />Keith