Mercruiser Ignition Fuse Blowing

Eric French

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May 5, 2020
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I have a 2010 Searay 185 Sport with 4.3tks. A year ago started getting intermittent issues with ignition fuse blowing. Driving me crazy. Have checked TKS Diode-its ok. Have checked TKS Module and it operated correctly. Have checked for issues around starter, etc and none found. Have noticed that Tach does behave a little weird with indicated RPM's jumping all around even though throttle is not being adjusted. At idle seems to be running rough and rich. Have replaced the slave solenoid, all ignition wires, distributor cap, rotor, and coil. Help.....
 

alldodge

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Howdy
The 20amp fuse has mostly 2 items which will blow the fuse, its the temp switch and the module. In most cases its the module

Use an ohm meter and measure the resistance of the module
70*F = 35-45 ohms
 

Eric French

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May 5, 2020
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Thanks for the response. The fuse I'm referring to is the 15a on the main panel under dash. One that feeds ignition switch
 

alldodge

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OK, then that can be many more things.
The purple wire feeds all the gauges and the motor. SInce your tach is showing some issues, disconnect the purple wire from it and see if that fixes it
 

Eric French

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May 5, 2020
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Many more is an understatement! I have both the owners manual and the shop manual and both leave a lot to be desired as far as schematics go. Thanks for the response it will be a couple of weeks before I can "get back under the hood."
 

achris

More fish than mountain goat
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May 19, 2004
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Tacho fluttering could indicate a short somewhere in a wire. And it could be anywhere. You are just going to have to go through everything. Check the harness between the instrument panel and the engine, and all of the wiring on the engine too. I once had a harness abrade through right at the back of the port cylinder head. Only found it because... the tacho was fluttering...

Chris.......
 

achris

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May 19, 2004
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Any possibility could be the ICM Module?

The Ignition Control Module module? Very very unlikely. Not impossible, but it would be one of the things at the bottom of my list...
 

Eric French

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May 5, 2020
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Thanks for the input guys. I'm in VA and boat is in NC. It will be about 2 weeks before I'm back. Pressure is building though. Memorial Day is official boat in water day!!
 
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