Mercruiser 5.0 EFI Low Voltage Issue

[davidpimer]

I have a 2015 Chaparral 310 Sig with two 5.0 MPI with DTS and Axius and Bravo 3 drives. Engine serial number is 2A440796. Port engine cranks slow and is not starting. Error message on display show Engine Misfire and Critical Low Voltage. The past two times I have used the boat, the starboard engine turned over quicker than the port, but the port engine would start and would run rough for a few seconds until it warmed up. Now the port engine will not start. It still turns over slow, but wont fire up. Thougt it was the battery, so I purchased a brand new battery. Turns over a little bit faster but still not as fast as STB engine. Still showing Misfire and Critical Low Voltage....Can anyone help me with this. I cannot get a mechanic for over three weeks due to availability. TIA!

 

[alldodge]

Since your cranking slow, I would start by looking at battery cables, battery switches/cables and their connections, both the battery and the block/starter.

Then look at the engine connector all for corrosion

Most the sensors use 5V coming from the PCM and it needs to be clean power (no fluctuations)

 

[davidpimer]

Could the alternator be the problem? It has a lot of corrosion on it. I’m thinking the diodes, brushes, or coils. Thank you for the reply.

 

[QBhoy]

Hi
sure sounds like a power issue. I’ve commented loads about my own mpi engine. At the start of the season if my battery hasn’t recently been charged fully...it will seem really healthy and turn the engine over seemingly well but not fire...until I let the key go. Then it will take a cough and a splutter for half a second. The fact is that these engines are so power reliant that despite seemingly decent cranking...if the battery is even a little weak or compromised by connections...the very action of cranking takes the power away from the engine enough to make it not even bother firing. When the key is let go and the load isn’t taken up by the starter..it momentarily thinks it has the power to fire just as you let go of the key. Bottom line. It needs a full and healthy supply to even think about firing.

 

[alldodge]

Could the alternator be the problem?

Not with the motor cranking

 

[davidpimer]

Thanks again for the info....I will be back at it tomorrow to get this figured out.