Starter, 90 amp fuse or something else?

[Boater71]

I've been having issues with STBD engine stalling at idle after a full day of boating. Low voltage error. I used a voltmeter and got he following results:

Key is in OFF position, batteries on

• Voltage at alternator is 13.3V
• Voltage form the 50 amp fuse is the same
• Voltage going to stater is the same

Key in the ON position, but boat has not started (i have a push button start), batteries on

• Voltage going to stater is the 13.7
• Voltage from the 50 amp fuse is 8.87 to 9.06 V
• Voltage at alternator (Orange wire) 8.87 to 9.06

I could not get to the starter as it is a very tough squeeze. Any thoughts here? What should my next step be? I called my mechanic and he said to replace starter, you would have to take out the manifold.

I have mercruiser 377 MAG MPI bravo.

 

[Boater71]

my engine is 2008 MX6.2 MPI Bravo III DTS with Axius and SeaCore

 

[alldodge]

I'm thinking corrosion and/or cable is loose. Need to remove cables at the starter, clean and reinstall.
Don't see an issue with the starter right now.

 

[Boater71]

Thank you. I did further troubleshooting today, i took the manifold, riser and elbow to get to the starter. I took the 90A out and this is how it looked like. Also, the power cable from the battery switch had no shield on it and was a bit corroded. how would the engine start if this is how the 90A looked?

 

[Boater71]

I'm thinking corrosion and/or cable is loose. Need to remove cables at the starter, clean and reinstall.
Don't see an issue with the starter right now.

Should i be changing the starter as well?

 

[alldodge]

The 90amp is used to protect the alternator if it shorts out. The motor will run but the ALT wouldn't work

It could be it was making enough of a connection to work and run but the rust and corrosion caused the starting issues

Clean everything up and reconnect cables. After connected try the starter to see if it cranks ok. Pull the kill switch so it won't start

 

[Boater71]

The 90amp is used to protect the alternator if it shorts out. The motor will run but the ALT wouldn't work

It could be it was making enough of a connection to work and run but the rust and corrosion caused the starting issues

Clean everything up and reconnect cables. After connected try the starter to see if it cranks ok. Pull the kill switch so it won't start

Thank YOU. i changed the starter and 90A. voltage now at the alternator is the same as the battery and the original 90amp corroded enough bu functional. I started the engine and voltage rev to 2000 rpm. The voltage at the alternator went all the way to 13.4 - 13.7, but not 14.2 like the other engine. Before changing the starter and 90A, the STBD would always stay around 14.2. i have not test the boat in open water yet, This was just revving the engine at the dock. i always compare the port and STBD. Here is what i got:
Key in and in on position
- STBD12.7
- Port 12.7
engine started:
- STBD 12.7
- Port around 14.2

Revving:
- STBD 13.4 - 13.7
- Port 13.7 - 14.2

I did clean with a copper brush all the connections involved and applied Dielectric grease to all the connections.

Is this normal or do I have another short which i need to troubleshoot?

 

[alldodge]

The bad connection probably caused some damage to the regulator in the ALT. It only takes an instant to damage the ALT if the wire becomes disconnected, like from corrosion

 

[sam am I]

Key in and in on position
- STBD12.7
- Port 12.7
engine started:
- STBD 12.7
- Port around 14.2

Revving:
- STBD 13.4 - 13.7
- Port 13.7 - 14.2

My $.02...........

I think you got it, it's just the STBD battery was maybe a bit more discharged (or maybe the battery is crappier now more then before due to age, running low etc) and after you run it and get it better topped off with full'ish charge, thinking it'll start to act same as Port.

Too bad we took out the ole current meters we used to have back in the day...........