Loss of Electrical power to dash

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
I have a Mercruiser 5.0L MPI Bravo 3. This past Saturday, I killed my batteries while playing music all day. I got a jump and got the boat started. I noticed when I took off that the boat seemed to lack the normal power. About half way back to my destination, I noticed that the battery gauge was acting erratically (going up to 16V and then back down to 12/13V). As soon I got near to dock to pull the boat onto the trailer, the boat shutoff. I then had no power to ignition or dash switches. Any ideas? Should the 50A circuit breaker be all the way in or out?
 

WrenchHead

Petty Officer 2nd Class
Joined
Feb 15, 2009
Messages
120
Generally breakers should be in. They pop out and you push them back. Sounds like you fried your battery. A battery can die in a NY minute. If you have a spare battery put it in the boat and see if that fixes your problem. If no spare battery then have your battery tested. You always start troubleshooting electrical circuits with a known good battery.
 

Krichbourg

Petty Officer 1st Class
Joined
Nov 12, 2009
Messages
231
Your battery may just need to be fully charged. When you got the jump, your motor was started from the power coming from the battery that jumped you. Your battery was still dead at that point and was being recharged during your return trip. A trickle charger is not that expensive and is a good thing to have for just such occasions. Good luck.
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
I did charge the battery up yesterday to around 50% and still no power to dash. The 50A breaker is popped out but I can't press it back in.
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Check the voltage at both sides of the 50A breaker today. Reading battery voltage. The Yellow/Red wire on the slave solenoid is reading 0V when both in the off position and run position. When I place the ignition switch in the run position (1 click clockwise), the voltage at the Red/Purple wire at the slave solenoid is down around 2.2 volts and both sides of the 50A breaker are around 2.2 volts. When in the off position, the connections are battery voltage. Thoughts?
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Back at boat troubleshooting last night. With the key switch off, I'm reading battery voltage on both sides of the circuit breaker, red/purple wire from starter to slave solenoid, and the battery and ignition connections on the key switch. The Yellow/Red wire at the slave solenoid and key switch reads 0V. Also, all fuses under the dash are good and have power going to them.
When the key is turned one position clockwise to the "on" position, all the locations mentioned above are only reading approx. 2.25 volts; however, the measured voltage across the battery terminals is still good. The Yellow/Red wire still reads 0.
When I turn the key to start, all the connections are reading 0V.
While in "on", I connected a jumper wire from the positive terminal on the battery to to the small Yellow/Red connection on the slave solenoid and got nothing but sparks. I then jumpered from battery positive to the larger Yellow/Red connection and the engine began to crank.

Could all this be because the slave solenoid is bad?
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
1) Measuring voltage at both sides of the circuit breaker SHOULD show battery voltage regardless of the key switch position. That's because the breaker is positioned way before any juice gets to the key switch.
2) You said the battery "B" and ignition "I" connections both show battery voltage with the key switch OFF. That is not correct. In the OFF position, battery voltage should be present only on the "B" terminal. In the RUN position you should see battery voltage on both the "B" and "I" terminal. In the START position you should see voltage on the "S" (solenoid) terminal of the switch.
3) All the fuses at the console have no bearing whatsoever on the issue you are seeing because they are fed by the "boat harness" -- not the "engine harness".
4) A battery that is charged to 50% should not read 12.6 volts which is what a fully charged battery should show. A 50% charged battery is worthless so when you turn anything on, voltage drops accordingly and hence the solenoid and any relays cannot function.
5) Charge the battery fully.
6) When fully charged, leave the negative probe on the negative terminal of the battery and begin following the juice from the positive terminal. A wiring diagram for your power plant will be the best tool for this so you don't continue to run in circles.

Without re-reading this entire thread, I trust you have disconnected, thoroughly cleaned (as in shiny bright) both ends of each battery cable, reattached them -- tightly and that you indeed have a fully charged battery and that the battery can actually "hold" a charge.
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Ok. It was my mistake on the "I" connections showing battery voltage in OFF. I checked again and that;s not the case. Why would I be reading battery voltage while in OFF but when the key is turned to RUN, the voltage at both "B" and "I" drop to approx 2.2 volts? I checked connections and they are good.
Also, when I said I measured battery voltage, I meant the battery voltage at 50%. The voltage I measured across the battery was the same at the switch and breaker.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Did you miss point #4 above? 50% is essentially a dead battery. When you turn anything on whatever voltage was available with no load, drops significantly when a load is added.
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Got it. Sorry. I'll charge the battery and have it load tested and try again. I'll post the results.
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Ok. Purchased and installed a brand new battery. When key is in the 'OFF' position, I have voltage readings as follows: 11.25V at both sides of 50A circuit breaker, 11.25V at the red/purple wire at slave solenoid and 11.25V at the Orange wire on the alternator. 10.8V at the battery connection on ignition switch.
In the 'RUN' position, I am reading around 2.25V at all locations mentioned above.

However, if I disconnect the red/purple and purple connector from the alternator, I read a full 12.6V at all of the locations mentioned above when switch is in 'OFF' and around 2.6V while in 'RUN'.

I ran a wire from the battery positive to the accessory connection on the back of the ignition switch and all accessories came on and worked. I also turned the key to the start position and touch the yellow/red wire connection with the wire from the battery and the began to turn over.
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Did more troubleshooting last night. Swapped out the alternator and ignition switch. Problems still exist. Still reading 2.25V at 'B', 'I', and 'A' when switch is in RUN and reading 0V at B, I, A and S when in start.

One interesting thing to note. While in RUN and reading 2.25V at the key switch, I flipped the kill switch to the OFF position and the voltage spiked up to around 8.4V at B, I and A. Is there some type of ignition relay that could be bad?
 

bengaltiger14

Seaman Apprentice
Joined
May 14, 2012
Messages
48
Problem solved. It was a loose connection at the 90A fuse on the starter. Apparently the connection has been loose for a while because black boot insulator at the fuse had melted. I'm thinking that was because of the loose connection drawing too much current; therefore, causing the wire to heat up?
 
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