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Major Electrical Issues
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Author:  NickH [ Mon Sep 21, 2015 9:32 am ]
Post subject:  Major Electrical Issues
Hi all, sorry for the novel...

So a few weeks back our alternator belt shredded on our 1996 5.0FI motor which is apparently a common issue. I replaced the belt and found our 2013 AGM battery (that was inadvertently shrink wrapped in the boat over the BRUTAL Maine winter by our fiberglass guy) was probably toast.

I swap batteries with a known good battery from another boat at our camp. The boat runs fine. We replaced the battery with a new one and immediately noticed the alternator was not putting out (voltage gauge on cluster and on Garmin GPS stayed between 11-12 volts). Thinking the alternator may be bad I order a new one of those too...

Fast forward to this past Saturday. We have a new battery installed, I install the new alternator, make up all the connections and everything seems fine. The boat warms up to temperature without issue. We take it easy heading down to the bay, everything is fine. The gauge on the cluster and Garmin GPS are both right at 14.4 volts, perfect! I bring it up to about 30 MPH and we're heading out for the day UNTIL...... about 5 minutes later I notice that the voltage gauge on the cluster is pegged and the Garmin is reading 22 VOLTS!

Uh-oh! I immediately idle the boat down, we're a mile or so from the boathouse. I vary the throttle a bit to troubleshoot and notice that the voltage directly fluctuates with the engines rpms.
At idle/headway speed I can get the voltage down to 15-16, not ideal, but not high enough to really fry anything. We make the long limp of shame back to the house on a beautiful New England Saturday. We get tied up and I shut down the engine. As soon as I do, the GPS dies and when you turn the key NOTHING happens. The battery appears to be connected correctly, I was so fuming mad at this point I don't check the alternator connections and simply put the cover on and walk away (as opposed to pulling the drain plug and walking away :shock: )

Anyways, long story short, has this happened to anyone? Does anyone have an idea of where I can at least START looking for the issue? Finally, I assume my new battery is probably junk, though since the boat and all of it's electrical systems ran fine I assume the ECM for the Ford EFI system is probably fine at this point. Any documentation I can find on the voltage regulator is vague at best, but I suspect this and/or the new battery may be part of the issue.

Thank you in advance for your help!

-Nick
Author:  GottWhat [ Mon Sep 21, 2015 11:06 am ]
Post subject:  Re: Major Electrical Issues
Here is a test from my Mercruiser Manual. It is a different engine and model than yours but I believe the testing procedure should be the same...

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Author:  230 Mike [ Fri Oct 09, 2015 11:32 pm ]
Post subject:  Re: Major Electrical Issues
Any updates?

Was your replacement alternator new or rebuilt? There are a lot of rebuilt alternators out there that have had nothing done to them but a cleanup to make them look nice. It's one of the reasons we used to rebuild them ourselves. This does sound like a voltage regulator problem.
Author:  NickH [ Mon Jan 11, 2016 9:41 pm ]
Post subject:  Re: Major Electrical Issues
230 Mike wrote:
Any updates?

Was your replacement alternator new or rebuilt? There are a lot of rebuilt alternators out there that have had nothing done to them but a cleanup to make them look nice. It's one of the reasons we used to rebuild them ourselves. This does sound like a voltage regulator problem.


Thanks for checking in, I didn't realize that I never updated this post... Basically I think it was a comedy of errors. The battery in the boat was definitely bad, but I also think the replacement (new, not reman) alternator was bad. I cleaned and checked every connection on the boat it seems and everything looked good. Long story short, at the end of the day I ended up having the old alternator tested. It checked out fine so I reinstalled it in the boat, found a virtually hidden 60a breaker popped on the engine and reinstalled my new battery after giving it a good, full charge on the charger so the alternator wouldn't strain on start up. The boat ran good as new well into the fall. Even with the extreme voltage spikes, nothing in the boat seems any worse for the wear.

One of my winter projects is going to be a new dual-battery setup and new battery cables all around. After 20 years, I suppose it's due.
Author:  LouC [ Mon Jan 11, 2016 10:29 pm ]
Post subject:  Re: Major Electrical Issues
Nice follow up. I had some issues with over charging that I cured by re wiring the alt sense wire. Before it was at 15.5 V after I was done it was at 14.4 which is more like it.
I got this tip when I replaced the OE alt with an Arco and this was advised in the instructions.
Lessons learned:
Always check your voltage at the batt with a good digital volt meter. The dash gauge may read lower than what the batt is actually getting due to resistance in the dash wiring on old boats. The sense wire on my OMC was also wired through the dash wiring and for the same reason (resistance) it was reading low and causing the alt to over charge. So I disconnected the original sense wire in the harness at the alt and taped it up. Then I ran a jumper wire from the B+ output on the alt to the orange wire terminal on the alt coming from tha batt. This lowered the charging volts from 15.5 to 14.2.
Next it you have a Garmin with the auto on function turn it off. Because this feature will allow it to turn itself on even if everything on the boat is off but the batt switch is on. It can drain a batt over a few days.
The dual batt system is a great upgrade. I did that about 10 years ago with all new cables.
Author:  Graham R [ Wed Jan 13, 2016 5:51 pm ]
Post subject:  Re: Major Electrical Issues
LouC wrote:
Always check your voltage at the batt with a good digital volt meter. The dash gauge may read lower than what the batt is actually getting due to resistance in the dash wiring on old boats. The dual batt system is a great upgrade. I did that about 10 years ago with all new cables.


I agree entirely.

I always regard everyday dash gauge readings as normal for that boat/ vehicle etc , not absolute values . So if the dash gauge reading changes, something is not normal.

If rewiring a battery circuit, buy one of those Ebay hand operated hex hydraulic crimpers; they work really well and making neatly crimped battery cables with heat shrink wrapped ends has a feel good factor ( for my 2009 boat, I got so fed up with the battery drain problems I rewired the whole battery and charging system; ended up with about 30 feet of spare heavy gauge cable from the original set up !)
Author:  NickH [ Sun Jan 17, 2016 7:20 pm ]
Post subject:  Re: Major Electrical Issues
I agree on the dash gauges, that's why I was alarmed when the Garmin (53DV with voltage readout) showed high voltage. I was able to confirm it with my multi-meter. I'm lucky, my company's shop (and where I store the boat in the winter :D ) is a fully equipped 12v shop that upfits public safety vehicles, so I have access to just about any mobile electrical tool I'd ever need... That is if they let the sales manager actually touch the tools...

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