Electrical Issues 8.2 mercury Horizon

[EMaughan]

I have a 2008 EPIC 23V wake boat and am having electrical issues. I was using the boat and all of a sudden it went into shut down and gave me an error code on the Mercury gauges - it states low voltage and the voltage dropped to 11-12 Volts (varied minute by minute). Two other error codes also, one was throttle position sensor not working and the other was starting sequence not successful.

I replaced batteries, cleaned battery switch and accessible connections. I’ve had two boat mechanics plug in and check codes, we found that one of the fuses for one of the O2 sensors was blown. We replaced and the boat started, then fuse blows within 20 seconds. We replaced all O2 sensors and fuse no longer blowing.

Still getting low voltage error and boat wouldn’t start. Back to the mechanic, no luck. Recommended that I take it to a marine electrical specialist to check the system out. He found a bad wire to O2 sensor, he fixed that. When testing each component he found that the ECM had a short inside and needed to be replaced. Ouch, got that replaced and the boat started fine, no more errors, great voltage… that is for about 30 minutes. . This time we were running at 2,800 RPMs and the motor started cutting out 3-4 times a second a part or so, and then it shut off. Now it is doing the same thing with the low voltage error again

Not sure what to do next. Any ideas? Marine electrician said they will look at it but the cash register keeps rolling.

 

[EMaughan]

Photos of motor and gauges

 

[alldodge]

Geezers you had it ruff, and have yet to find a Merc certified mechanic. Lots of shade tree Mechs. Most likely your original PCM has nothing wrong with it

What is the motor serial number?

Measure the voltage at the Bat before starting and after starting. Then measure the voltage at the alternator output orange lead while motor is running

 

[EMaughan]

Geezers you had it ruff, and have yet to find a Merc certified mechanic. Lots of shade tree Mechs. Most likely your original PCM has nothing wrong with it

What is the motor serial number?

Measure the voltage at the Bat before starting and after starting. Then measure the voltage at the alternator output orange lead while motor is running

Thanks for responding!
Motor Serial Number is 2A033979
The boat won't start now, says it doesn't have enough voltage at the gauges - doesn't even start the starting process. However, I show 13 volts at the batteries when I meter.
When it was running I was getting 14 volts at the alternator.

 

[alldodge]

Do you have 13V at the starter post?

 

[EMaughan]

Do you have 13V at the starter post?

 

[EMaughan]

Yes

 

[alldodge]

Seeing you have DTS, does the boat also have Axis?
If it does need to look for a trim sensor fault. If the trim sensor has an issue the motor will not be allowed to start because the PCM doesn't know where the drive is.

 

[EMaughan]

Seeing you have DTS, does the boat also have Axis?
If it does need to look for a trim sensor fault. If the trim sensor has an issue the motor will not be allowed to start because the PCM doesn't know where the drive is.

I'm not sure what Axis is... my boat has one trim tab in the middle of the boat.

 

[EMaughan]

Here are some misc. photos...

 

[alldodge]

ok, its a single engine boat so it would not have axis. Also being an inboard it would not have a trim sender

With gauges not coming ON then need to check voltages at the gauges. If no power then kill switch, breakers, fuses

Neutral safety switch

Need a scanner with these new motors to get anywhere these days. Vessal View isn't bad but it will not indicate everything that is going on
https://www.rinda.com/marine/marinemenu.htm

 

[EMaughan]

ok, its a single engine boat so it would not have axis. Also being an inboard it would not have a trim sender

With gauges not coming ON then need to check voltages at the gauges. If no power then kill switch, breakers, fuses

Neutral safety switch

Need a scanner with these new motors to get anywhere these days. Vessal View isn't bad but it will not indicate everything that is going on
https://www.rinda.com/marine/marinemenu.htm

All gauges and dash lights come on, just says there is low voltage and that the motor startup process will not function. The first pictures of the gauges I uploaded is what the gauges are doing right now when I turn the battery switch and try to turn the boat on.

 

[alldodge]

ok, a boat gauge may not be accurate. I'm seeing 12V on the gauge which should be enough to at least try. Its not trying so the PCM is seeing voltages lower. It could be on the 12V side or the 5V side.

Sensors use a 5V circuit coming from the PCM. Would need to measure voltages at the TPS, water pressure, crankshaft or MAP

Measure power at the helm key switch Red/Purple wire with key off. Leave meter there and turn key ON and see if voltage drops. Then measure power on the purple wire with key ON