Where to start? Ignition issue

mdolesh

mdolesh

Active Member
Dec 18, 2019
432
Edgewater, MD
Boat Info
370 Venture 2013
Twin 300 L6 Verados

- Previous boat: 290 Sundancer 2006
Engines
...
Good morning everyone. I am sadly back at work this morning but had a great 4th of July, I hope everyone else did as well! So here is my issue...anchored out all day yesterday. I have 3 batteries, 1 for Stbd motor, 2 for house, port motor, etc with a selector switch for 1, 2, or both. When we got to our spot I turned off the starboard single battery and switched the dual bank to 1. Had a great day, went to leave and got nothing from the port motor, gauges, ignition, no beep, nothing. (I did leave both refrigerators on but that was the extent of our power consumption). I switched back and forth between 2 and then both and still nothing. Tried the emergency crossover and the finally port gauges lit up but the motor would start. Limped home, trying the crossover a few times, but no luck. Docked and plugged into shore power/battery charger while cleaning up. An hour or 2 later, still nothing at all from the port ignition and gauges, everything dark, no beep, nothing. My question(s)...1. Where to start with the diagnosis? 2. Why would the emergency crossover start the port motors? The starboard battery was full and strong. Thanks guys!
 
Batteries are 1.5 years old. Engines are 5.0MPI Mercruisers.
 
Did you check the 50 amp breaker on the engine?

They are not the best, and are sometimes hard to tell they tripped. Push in firmly and retry.
 
CaptRonn said:
Did you check the 50 amp breaker on the engine?

They are not the best, and are sometimes hard to tell they tripped. Push in firmly and retry.
Click to expand...
Yes. I tried that and it seemed normal when compared to the other engine. However... I didn't really press it hard. I will try that again.
 
So your year schematic for a SINGLE engine shows a 1-both-2 switch for the two primary (house) batteries.
With charger breakers #1 and #2, so the two batteries should not be cabled together at the positive posts.
(no jumper on +)

The schematic for the TWIN engine simply shows an extra on-off switch for the starboard engine.
and charger breaker #3 for that battery.

Dockside the convertor AC breaker needs to be on AND the three DC charger breakers (30A) must not be tripped to get charged back up.
For engine charging there is the 50A and many Mercruisers also have a 90A fuse at the starter for everything.

So with the switch on #1 you should have only drained #1 at anchor.
But when you went to "both" you had no power. So battery #2 was also dead.
To use the jumper solenoid you need to start the good engine first, since the other is dead the jumper switch uses the ignition power from whichever is good. It wont work with the good ignition off.

Test light and voltmeter needed.
Start with checking all the grounds at the batteries and the grounding buss, engine blocks.
Check that the AC convertor is on, and the three DC breakers are good.
With the battery switches Off, you should see the charging voltage at each battery (13.5-13.8). If not fix that first.
The charger goes directly to the battery terminal on the battery switches, plus ground.
If that's good see if all the batteries charge back up.
You can't leave them dead long without suffering sulfate damage.

Then turn the convertor off and test the #1 and #2 batteries separately with a bit of load, they should hold voltage.
About 12.5 at rest fully charged. 12 or less is bad. Under light load should stay around 12.4 and drop very slowly.

Let's assume the batteries come back up and are good for now.
Then start troubleshooting the jumper system and the engine systems.
 
hughespat57 said:
So your year schematic for a SINGLE engine shows a 1-both-2 switch for the two primary (house) batteries.
With charger breakers #1 and #2, so the two batteries should not be cabled together at the positive posts.
(no jumper on +)

The schematic for the TWIN engine simply shows an extra on-off switch for the starboard engine.
and charger breaker #3 for that battery.

Dockside the convertor AC breaker needs to be on AND the three DC charger breakers (30A) must not be tripped to get charged back up.
For engine charging there is the 50A and many Mercruisers also have a 90A fuse at the starter for everything.

So with the switch on #1 you should have only drained #1 at anchor.
But when you went to "both" you had no power. So battery #2 was also dead.
To use the jumper solenoid you need to start the good engine first, since the other is dead the jumper switch uses the ignition power from whichever is good. It wont work with the good ignition off.

Test light and voltmeter needed.
Start with checking all the grounds at the batteries and the grounding buss, engine blocks.
Check that the AC convertor is on, and the three DC breakers are good.
With the battery switches Off, you should see the charging voltage at each battery (13.5-13.8). If not fix that first.
The charger goes directly to the battery terminal on the battery switches, plus ground.
If that's good see if all the batteries charge back up.
You can't leave them dead long without suffering sulfate damage.

Then turn the convertor off and test the #1 and #2 batteries separately with a bit of load, they should hold voltage.
About 12.5 at rest fully charged. 12 or less is bad. Under light load should stay around 12.4 and drop very slowly.

Let's assume the batteries come back up and are good for now.
Then start troubleshooting the jumper system and the engine systems.
Click to expand...
Thank you! I am heading down to the marina today and will start the troubleshooting. I really appreciate all the input! I will follow up with my findings.
 
I just read that a few times. I have twin engines and I stared the starboard and then tried the port with the emergency jumper and got nothing when port was on 1, 2, or both. Starboard battery was at 14.1 when running the engine and it was strange that it wouldnt jump over. Definetely could be a breaker somewhere or a ground. I will do some digging. Thanks again!
 
Ok..all three batteries are 13.2-13.4 when I unhooked everything and put a meter on them. Still zero when I turn the port ignition on. No beep, nothing. All the breakers look in place. Suggestions on next steps?
 
this might sound totally out of the box, i repaired a toyota van for a coworker and he said 3 different electricians had looked at his car ( dark and dead ) and all said " checked the grounds and all are good " when i got there all grounds were good. so i used a jumper wire from pos+ terminal to where the positive cable ended at a junction under the driver seat. The car started right up. he needed a new positive battery cable . id check and see if there is 12 volts going to the starter/solenoid with your key/switch in the on position for that engine. the new cable completed the circuit for all his gages and lights .....worth a investigation to find out where the flow of electrons stops
 
Batteries are fine. They power the bilge pump, blowers, etc when only the port bank was connected. I swapped rocker switches at the helm and ruled that out also. The 50amp breaker on the engine seems fine. Is there some other breaker? One other thing...If I hit the emergency start button and then the port ignition, the gauges do come on and I just hear a click when I press the switch but doesn't start the engines.
 
Last edited:
Look for a 90 A fuse at the starter
If no voltage at the back of the 50A

could be a burnt battery selector switch or lose connections on back
 
upload_2021-7-5_20-11-23.jpeg
 
Mercruiser added that fuse around 2005/6 because they had a few fires due to the alternator, alternator feed wire and or the the feed to the 50A breaker shorting.
It’s a PITA to get to and change
Simple way to test is to see if you have 12v at the back of the 50A when battery switch is on
 
Will do! Thanks for the advice!
 
Is the click you're hearing from the starter solenoid or somewhere else? A lot of times a starter can have a dead spot and you'll only get the solenoid click. If you whack the starter with a hammer you can get it going usually, but sometimes it takes a good whack. If that's the case, I'd probably replace the starter. Another way to check that is to put a voltage meter on your starter and see if you're getting power when you turn the key. You'll need a second person ideally for that. Another option is get a remote start switch. It bypasses any solenoid or switches and puts power directly to the starter when you hit the switch. It's mainly used for working on engines. It'll narrow things down for you.
 
You must log in or register to reply here.

Forum statistics

Threads
113,143
Messages
1,427,197
Members
61,057
Latest member
DrBones!
Back
Top