Alternator and fuel pump on Volvo Penta 3.0 GLP-D

[kwanza1]

After doing some fixes to my cooling system, I took the boat for a test ride.
One of the first out-of-ordinary issues I noticed straight after launching and starting engine was that my dash voltmeter was indicating 12 V, while it usually indicates 14 V. The battery was charged, having spent the previous 24 hrs on a charger.
Other gauges behaved as expected, but the dash voltmeter would not go above 12 V.
After approximately 7 km / 20 minutes of cruising on a flat water, with ~22 knots, ~3000 RPM, my engine suddenly shut down, and I was not able to restart. Cranked, turned over, no start. Checked for spark, it was OK. the cut out was surprisingly brisk, not loosing power and slowly dying out, but almost very quick shut-off. My fuel gauge indicated half tank, as expected, and I added more fuel once arrived home, as a check. All fuses seem intact, did not check relays.
Fuel filter is approximately 2 years old.

Is it possible that my dead? alternator impedes fuel pump to function?
I did disconnect what I think is the fuel line into the carburetor and can't notice any fuel being pumped either while manually priming or attempting ignition. I am referring to the silver metallic pipe entering the carburetor on the left side of the image (flame arrestor removed only for these tests)
How can I check alternator in a no-start situation, or how can I check the fuel pump?
At ignition, I have a default alarm that only goes off after successful ignition, so can't really listen to the fuel pump....
Thank you for any suggestions.

 

[Grub54891]

Sounds lik your alternator is bad, but I would be removing and cleaning all battery connections completely, in clouding the grounds on the block. Get a hand held test meter, charge the battery fully, test battery before starting, then test after startup, you should get 13-14 volts from the charging system.
Anything less than 12 volts will cause sudden shut down as you describe.

 

[alldodge]

@kwanza1 noticed in your first post you mentioned that you were unable to get into your original account. Guessing it was @Kwanza so maybe @tpenfield can assist

I don't have a wiring diagram for your exact model but do have one for GL-E which also uses the EST ignition. With the ALT not working this can mean power is not being supplied to the fuel pump when running (green wire and Diode).

No fuel being seen when cranking can mean power is not being supplied on the Yellow/Red wire, the other diode (23) has opened up, fuse (26 - 7.5 amp) blew, the relay (25) or fuel pump is defective.

Check voltages and fuse

 

[Lou C]

Agree with starting with making sure all the wiring is clean, not corroded at terminals,etc. If you have wing nuts retaining your battery cable terminals, get rid of them, they loosen and cause these problems, use locking nuts instead.
Don't forget the large cannon plug, these can get loose and cause problems like that. One time I had a no-crank, no gauges issue but my tilt n trim worked. Cause? an oxidized old school glass fuse in the main fuse box, cause was just oxidation impeding current flow. So, it doesn't take much.
I'd start by pulling out the ignition switch and checking for battery voltage between these terminals and ground:
B terminal (battery, red wire) you should have battery volts with the battery switch on
I terminal (ignition, purple wire) you should have battery volts with the battery switch on and the key turned to the first notch after off
S terminal (start, red/yellow wire) you should have battery volts when the key is turned to start.
some ignition switches have an ACC (accessory) position, but most older boats do not.
If this reveals a loss of voltage, you have to go back and find the source.
With battery cables they can rot under the insulation and cause high resistance, make sure the (negative) return path (we call it grounds, but it is really a return path for DC current) is as good as the positive side. Automotive non-tinned cables are junk in a boat, if that's what you have ditch those and start with new. On my boat I bolted marine quality automotive style clamps onto the cable ends, that way when they start to get too oxidized I can just bolt on new ones.