So I’m seeing an intermittent problem. Twin 7.4 mpi mercs. Engines run fine. Volts usually between 13-14. But every so often the voltage spikes to 15-16 and stays for a minute or two, then drops back. Happens on both engines at the same time. Gages have been verified with digital data via fox marine gateways. I’m thinking loose ground somewhere and will check that tomorrow or during the week. Any other thoughts or possibilities? Is it even an issue? Thanks in advance.
Voltage gage spikes
- Thread starter Golfman25
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- Mar 2, 2000
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Both spike at the same time? These are digital gauges? If you start one and leave the ignition on for the other do the voltages track? Is the dash/gauge cluster fed by a single internet style cable or are all of the analog lines connected to the dash?
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Boat/Engines are 1998 (MEFI 2). Both spike in unison. Be motoring along all fine and then they'll spike to 15+ volts for a min or so, then back to normal. Then repeat -- but the times seem variable. I bot the boat late last summer, and noticed it the few times I had out, but thought it was old gages (from 1998). This winter, I installed Fox marine gateways which feed the ECM data to my Garmin device and their own wireless app. Both the Garmin feed and the app match the gages. Digitally, each engine varies from each other by 0.1-0.3 volts or thereabouts -- so I am not getting the exact reading same reading for each engine. It looks like the gauges are fed by the engine wiring harness. I'll need to try one engine only -- but never noticed anything unusual.
I should also add that I have a voltage drop when starting the starboard engine which cuts out the stereo system. No clue if that is related or not.
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I assume I have an alternator on both engines, but will have to check to be sure. I have two separate battery switches under the cockpit sink -- one port, one stbd. Then there is one in the engine room for the generator battery.
And yes, the stbd battery primarily powers the main cabin 12v. The port side powers the electronics and control station. Each side has two batteries. Thanks for your help.
- Joined
- Mar 2, 2000
- RO Number
- 36
- Messages
- 6,625
It would be interesting to know if both of the port/stbd battery switches have a setting for both and if you run that way. If so try setting them to the engine they (primarily) service and see what happens.
Edit: if you have only one alternator that is not the best idea. But it does indicate that both are tied together. If both engines have an alternator run with the switches set to isolate each side from the other and see what happens.
Edit: if you have only one alternator that is not the best idea. But it does indicate that both are tied together. If both engines have an alternator run with the switches set to isolate each side from the other and see what happens.