If you loose an alternator, all you have to do to keep going is run the generator while underway, it’ll keep your batteries charged. We did that for 5 days while cruising Lake Superior a couple of years ago until I could get one shipped to me.
This was it. Thanks!
I work on 4 different 2001/2002 400DBs with Cummins here in coastal SC that live in salt water 24/7. All but one have had the rusted turbo bolt and turbo exhaust flange symptom. In all cases it was due to the mixing elbow eating away to create pinholes on the inside that shoot salty water back into the turbo. When the mixing elbow was removed the turbo had significant rust growth narrowing the diameter of its exhaust port. The fix was two fold. Had turbos rebuilt and replaced old mixers with new from D’Angelo made from INCONEL. Only way to find out is to take the mixing elbow off. We had to cut the rusted bolt heads off for most of ours.
Curious if its possible to scope the elbow to find out out. The elbows on the 42/44 DB is encased in a heat wrap.
Easy on a 400DB. Just remove the exhaust hose from the mixing elbow then you can scope all the way back to the turbo. I don’t know anything about the 42 exhaust setup so not sure what you have for a mixer.
The “ignition switch” you turn on on the bridge before you hit the starter provides the 12V for the fuel solenoid to provide the fuel to the engine and cuts off the engine when you turn the switch off. However, the 12V signal goes through some other circuits first, like the Halon system to cut off the engine in case of fire. I had my engine cut off one time during a run that turned out to be a defective diode that was located on a dummy plug as part of the engine harness.
I had them build me two new mixer elbows from 316L SST. Those were around $1800 each and that was four years ago. There were pin holes developing on the old ones and were original from SR. At the time I think there was around 1800 hours on the engines and now 2600. One of the most important things is to ensure all of the exhaust metal components are tied to the boat's bonding system as pin holes are galvanic corrosion.
$1400 each purchased in Oct/2019. Somewhere closer to the beginning of this thread are pictures. I’m guessing your elbows are noticeably larger than the ones I had made.
Quite a bit larger and has insulation on the hot section. I'd hate to purchase them today....
Coming back from a trip yesterday and noticed that my voltage reading was way below 13v on one motor. Immediately thought of this post. Turned on the gen to get the volts up and when back at the dock I checked via my Victron shunt and confirmed that the alternator is not charging the battery when the motor is running. Alternator is only 2 seasons old. Thinking there is a loose connection somewhere. However if connection was loose and alternator was not delivering power to the battery is the alternator now shot? Heading back to the boat today to do further investigating as we got back late in the evening.
Quite possible. If the alternator is driving current and it is disconnected (loose connection for example) it will take out the alternator's rectifiers. And quite possibly other electronics. A significant voltage spike occurs when the output current from the alternator is interrupted.
Thanks for the reply @ttmott. So if alternator is shot no harm in reconnecting a loose wire (if that is the case) and just running the gen until end of season when I can address? No telling how long its been like this as we normally run with the gen on.
The issue that can happen is if the diodes in the rectifier circuit allow current to flow in the wrong direction. Diodes are electrical "check valves" for lack of a better description, current can flow one direction but not the other. They can fail Open or Shorted. If they are shorted then current will flow from ground to the battery positive and will discharge the battery. You can usually tell as the back of the alternator gets hot to the touch when not running.
