Low Voltage - Engine Voltage is low

Osama

Recruit
Joined
Nov 14, 2020
Messages
1
I have a 2008 Mercruiser 350MAG. Engine SN 1A324453 (sorry long read - new to boating so the terms maybe confusing)
A week before the issue began I had a one-off sys fault "Engine Sensor" but everything was working fine. The problem(s) then started one day after turning the engine off after a day in the water, a long continuous beep alarm with a message that read "Low voltage - Engine Voltage is low - battery !" The engine wouldn't attempt to start at the first, but after turning the batteries off and on a few times, it did start but with bad cranking noise (to flush the engine)
Next day, it started fine but in the water when I switched the batteries to on, the same long beep and the engine wouldn't start for about 10 mins. When the mechanic diagnosed it, the low voltage did not appear (both batteries read 11.4 when off 14.5v when on) but lot of cranking so replaced the starter.
The following week, the engine would only start after a few attempts and the low voltage came back. He figured the start/stop button in the lever was faulty and was cutting off the power to the engine (as when he connected a direct cable to the battery, the engine started right away without cranking) so I need to replace the entire lever and low voltage was due to the solenoid was receiving 14v but only 8v was going to the engine) so he cleaned it and the issue went away.
Few days later, the low voltage issue came back, NOTE - it does not appear when undocking but only when once I turn the engine off in the water. Batteries are 3 months old
Before sending it to the dealer for a proper diagnose, wanted to share the experience for any assistance would be appreciated.
Other one-off alarms I got in the past 2 weeks were "Start system may not start. The starter solenoid is not working properly" and "Start sequence aborted"
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,312
first, stop playing with the font
second, welcome aboard
3rd, you are reading low voltage, either from a bad connection at the batteries somewhere or bad batteries. anything below 12 volts is considered a dead battery. start by load testing your batteries and cleaning your connections until they are clean and shiny enough your mother in law would eat off them.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,348
Mpi are very sensitive to voltage. So much so that they can often turn over quite healthily but not try to fire.
worst case and thinking pessimistic...you may have signs of water ingress loading up the cranking or on the verge of hydro locking
 
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