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Electrical Issue - Thoughts?

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Old 02-26-2018, 02:45 PM   #1

96MariahZ220 is currently offline
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My Model: Z272 SHABAH
My Engine: 502 MAG MPI
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Default Electrical Issue - Thoughts?

I have a 1996 272 Shabah w/ the 502 mag. I have been having an electrical issue that has left me stranded and I wanted to run by the scenarios in which they occurred. I also read somewhere that in the earlier years Mariah wasn't up to par on their electrical systems? Any how below is what happened.

So my voltage gauge sometimes hangs around close to 10 volts and that seems to be when this issue occurs. More times than not it hangs around 13 volts which seems to be where it should when running. The first time this issue happened we plugged up a pump to blow up the tubes and as soon as I flipped on the pump the boat died and would not do ANYTHING. The only thing on the entire boat that works when I experience this issue is the trim for the outdrive, it goes up and down just fine. I had to get towed in when this happened.

This past weekend I got it out of the warehouse to go run it since it was 78 degrees (benefits of a bilge heater and living in the south). I fired it up in my driveway Friday evening and everything was great, volt meter was good around 13 volts. Took it to the lake Saturday it fired up but the volt meter was down close to 10... We hung out at the dock and it did not move and I decided to run the blower and as soon as I hit the blower switch... BOOM everything died except the trim buttons. I decided to plug up my batteries since I have an on board charger and tender and after about 30 minutes of letting it sit I got everything back and we ran all day no issues.

The weird thing about this as when it happened before I never hooked it up to charge it eventually came back miraculously and started working again after about 2 hours.

No blown fuses when this happened! I've checked every connection and ground possible so I am at my whits end here... What the heck is going on!
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  • Old 02-28-2018, 03:47 PM   #2
     
    Hudson River Steve's Avatar

    Hudson River Steve is currently offline
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    Default Re: Electrical Issue - Thoughts?

    You definitely have a bad connection(s) somewhere. The voltmeter with the engine running should be close to 14V and never around 10V. If it is reading anything below 14V with the engine running and your alternator is OK you are experiencing a substantial voltage drop in either the B+ or B- line coming up to the helm. I suspect that your voltage drop is enough that your ECU is turning off.

    I would suggest that you use a DMM set to read voltage and place the black, negative probe of the DMM on either the battery B- line or to a clean connection on the engine block. BTW - If you haven't already cleaned all the black B- terminal connections from the battery to the engine block you should start there. If you can get it in a no run condition, measure the voltage on the purple wire (Pin 5) on the engine side of the big connector on the engine. Note, leave the connector plugged in so you will need a pin or needle to pierce the insulation of the wire. If this voltage is below ~9-10V the ECU will not operate correctly and you will not get any fuel.

    There are many places were you could have a bad connection. I would start probing with a DMM at the ignition switch B+ terminal, remember to leave the DMM (-) wire on the battery/block for all readings. Turn the ignition switch to run and measure the voltage on the I terminal of the ignition switch. Keep going down the line, next is the output of the safety switch on the shifter. You can measure this at Batt terminal on one of the gages. You will need to get a copy of the Mercruiser schematic for your engine and just trace the flow of current from the ignition switch to the ECU.

    Happy hunting.
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    Old 03-01-2018, 02:49 AM   #3
     
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    Default Re: Electrical Issue - Thoughts?

    Shortly after buying my boat last year, I noticed the same indications: 10v on the gauge a lot of the time even though the battery was fine. I found the problem to be the fuse block, which was probably the original one (18 years old). I could wiggle the very loose ignition fuse around and make the instrument panel voltmeter go up (12v+) or down (10v). Replacing it was easy and only cost about $15. I did not have the more extreme symptoms like engine or accessories shutting off.
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    Old 03-06-2018, 02:09 PM   #4

    96MariahZ220 is currently offline
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    Default Re: Electrical Issue - Thoughts?

    Quote:
    Originally Posted by Hudson River Steve View Post
    You definitely have a bad connection(s) somewhere. The voltmeter with the engine running should be close to 14V and never around 10V. If it is reading anything below 14V with the engine running and your alternator is OK you are experiencing a substantial voltage drop in either the B+ or B- line coming up to the helm. I suspect that your voltage drop is enough that your ECU is turning off.

    I would suggest that you use a DMM set to read voltage and place the black, negative probe of the DMM on either the battery B- line or to a clean connection on the engine block. BTW - If you haven't already cleaned all the black B- terminal connections from the battery to the engine block you should start there. If you can get it in a no run condition, measure the voltage on the purple wire (Pin 5) on the engine side of the big connector on the engine. Note, leave the connector plugged in so you will need a pin or needle to pierce the insulation of the wire. If this voltage is below ~9-10V the ECU will not operate correctly and you will not get any fuel.

    There are many places were you could have a bad connection. I would start probing with a DMM at the ignition switch B+ terminal, remember to leave the DMM (-) wire on the battery/block for all readings. Turn the ignition switch to run and measure the voltage on the I terminal of the ignition switch. Keep going down the line, next is the output of the safety switch on the shifter. You can measure this at Batt terminal on one of the gages. You will need to get a copy of the Mercruiser schematic for your engine and just trace the flow of current from the ignition switch to the ECU.

    Happy hunting.
    Thanks - I just had my alternator rebuilt yesterday because i believe this is the issue and the shop told me it was def. "failing"... We will see... it is the original one at 22 years old and its only costing $65.00 for the rebuild. I am still going to hit all my connections that you have mentioned and clean up all the grounds on the engine block and work my way up... going to be fun!
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    Old 04-06-2018, 02:39 PM   #5

    96MariahZ220 is currently offline
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    Default Re: Electrical Issue - SOLVED - update

    Just thought I would update you guys on this. The problem is fixed and it wasn't a ground issue or anything as all that looked good. I took it to someone a friend referred me to who is a 30 year mercruiser veteran/mechanic for the local Sea Ray dealership and he also does side work on boats at home and is an electrical genius and he found the problem. The main power wire that feeds into the ignition circuit breaker on that little panel was shorting out. That is the breaker that everything else "piggy backs" off of up at the helm for power. He ran a new main power supply wire from the battery to that breaker panel and now i am getting 12 volts everywhere at the helm like i should now. Now some of my gauges are working correctly now that were never right from the day i bought it. Maybe this can be useful to some of you out there who might be experiencing a voltage drop issue at the helm on gauges and switches... Start at the Ignition circuit breaker and if you don't have 12 volts there then chances are you won't have it elsewhere.

    Now on to a good boating season!
    Reaper22 likes this.
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