Alternator and fuel pump Volvo Penta 3.0 GLP-D

[Kwanza]

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 fully charged, having spent the previous 24 hrs on a smart 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 a full tank, 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 whole 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.

 

[Kwanza]

Update/temporary fix:

I measured the voltage between ground and each of the two brown wires connected to the back of the alternator, and there seems to be a problem here:
Brown wire (engine side): 0.03 V with key OFF, 12.5 V with key ON. This seems correct.
Brown wire with white stripe: 0 V with key both ON and OFF. Apparently this should always read 12 V.

Connected a fused line from battery plus terminal to the sensing port of the alternator (which shows 0 V, and it should show 12 V), started normally, and both dash voltmeter and multi-meter show 14 V.

 

[Kwanza]

An update for anyone who might be experiencing similar issues.
The culprit seems to be the blower, or some other component on the same circuit.

Blower, running smoothly, with ignition on notch 1 or 2 is knocking and keeping voltage shown on dash voltmeter down by ~ 2 V in most scenarios:
- on resting battery, from 12 V to 10 V
- on charging battery, from 13 V to 11 V
- on alternator, from 14 V to 12 V.
- Digital multi-meter connected straight to battery shows the correct voltage, i.e no knock down while dash voltmeter knock it down.
- on resting battery, with ignition on 0, no voltage knockdown.

No other accessory (bilge pump, nav lights, trim up/down) knocks it down. Flinches slightly at the trim, ~2-3V, but comes back.

Turning the blower off would not help.
Disconnecting the blower plug from the harness allows easy start, no need for 12+ jumper cable to the alternator.

Ensuing question is: what other (critical?) component might be on this same circuit as the blower? I usually start my engine with the hatch cover open, and while I have the blower running while out, I understand many people only have it on at start and when docking. So I could live with this for now.
I'm worried about something else being on the same circuit that I'll eventually need (i.e temperature alarm...) The rest of the gauges all show nominal values.

I also ended up with lots of cleaned and secured connections.