2001 Merc 150 Fuses keep blowing

[fishndoc7]

2001 Mercury 150 ser # 0T3720672 Harness assembly 15 amp fuses keep blowing and charging stops to batteries .The only way I know is that dash and gps gauge drops from 13.5 to below 12 volts and below. Engine running fine with no hesitation or misfires. Any ideas?

 

[CharlieB]

Re: 2001 Merc 150 Fuses keep blowing

The motor will continue to run fine as the charging system only shares the stator frame, the ignition is self-generating, comparable to a mag ignition, it does not need a battery to operate.

The battery is simply to make starting easier, V-6's are tough to rope start. Not impossible, but I haven't been able to do it.

A sick battery can draw excessive current and pop the fuse, or excessive load thru all the accessories powered thru the key switch.

One way to troubleshoot is use a 10 or 15 amp self-resetting circuit breaker in place of the 20 amp fuse, leave the motor cover off and LISTEN. With the key ON and the motor NOT running, start turning on all the accessories you normal use, LISTEN HARD for the 'click' of the circuit breaker tripping off and again resetting a minute later after it cools.

Turn off 'one' accessory and wait to see if the breaker stops tripping, if not, plug that one back in and unplug the next one, repeat until you can identify which item is drawing excessively.

Radios often have a constant power wire to keep preset stations in memory, many times this circuit starts drawing more than it should. Often this wire is fused separately in the radio wiring. Pull this fuse and see if the breaker stops tripping. Is so, either replace the radio, or leave the fuse out and set your station manually every time you turn it on.

 

[fishndoc7]

Re: 2001 Merc 150 Fuses keep blowing

There are 2 optima blue top deep cycle batteries that were checked and are now fully charged. After putting a 15 amp breaker in the center slot of the harness and the key on all the accessories including the bait well ,radio, gps , wash down, ,fish finder, bilge pump and lights were turned on and the breaker did not trip. The original fuses are 20 amp not 15 as I originally stated. Any other sugestions?

 

[sschefer]

Re: 2001 Merc 150 Fuses keep blowing

There could be a dozen things causing your problem and Charlie pretty much gave you the low down on how to eliminate most of them. One that wasn't mentioned was checking the nuts on the back of your gauges. Just have a look, you never know.

 

[Faztbullet]

Re: 2001 Merc 150 Fuses keep blowing

If its the fuse for the rectifier/regulator thats popping check that unit as it may be bad. Your motor should have 3 20 amp fuses, 1 for each rectifier/regulator and a Accy fuse.

 

[fishndoc7]

Re: 2001 Merc 150 Fuses keep blowing

Thank you for the ideas. Will check gauges and rectifiers this afternoon weather permitting .The last trip I tried to go out I watched the gps voltmeter readings. They started out at 12.2 and as I planed off they steadily went up to 13.7 before dropping back to 12.1 when the middle fuse blew.

 

[CharlieB]

Re: 2001 Merc 150 Fuses keep blowing

Optima are not the best batteries for marine applications.

Generally we want standard lead-acid which will allow higher charging voltages.

 

[fishndoc7]

Re: 2001 Merc 150 Fuses keep blowing

Took off the flywheel to examine the stator and connections to the rectifier/regulators. There were no signs of a problem until feeling the wire going to the regulator of the blown fuse and at a bend it felt spongy. Opening up the wire ? of the copper strands were broken at the bend of the wire. A friend took it to a shop and it was spliced, soldered and sealed. Today I took the boat out and the gps and dash gauges showed 13.7 -14.2 volts all day with no blown fuses. Thanks for your help and pointing me in that direction.

 

[Silvertip]

Re: 2001 Merc 150 Fuses keep blowing

Accessories should NOT be powered from the engine harness. The "A" terminal on the ignition switch is intended to feed only the gauges as the harness is not designed or intended to fuse a boat load of accessories. There should be a speparate pair (red - black) wires (#8 or #10 gauge) running from the battery to the fuse panel at the console. That is what powers other accessories such as live wells, GPS, radios, lights, etc. The fact that the voltmeter on the console remains operative when that fuse blows, proves this. The problem is in the circuit the blown fuse protects. Since we don't know which one you are talking about, we can't help much.

 

[snowman48047]

Re: 2001 Merc 150 Fuses keep blowing

My 2001 Merc 50 had a recall or whatever and the 20 amp fuse was replaced with a 25. That year there was an issue with that circuit. Check with Merc. or a Merc. repair shop and have 'em look it up. I had blown fuses and a melted harness.