'91 Volvo penta 740 (7.4L) randomly shuts off hard - Won't start now

[Rboucher111]

1991 Cobalt with Volvo 740, Holley carb, shut off a few times memorial weekend. Took it out this weekend and after running 10 min at idle it shut off again, and then few more times trying to leave the marina including when I was throttled up to accelerate. Turned around to add fresh gas. Refused to start after that except when we manipulated some linkage on the back left of the carb. That only worked once. No success starting since. So the situation has gotten progressively worse. Starter fluid didn't help. Had spark at one of the plugs. Can see gas being squirted in to the carb.

Historically Engine has run like a top. Never misses or rough idle. Starts easily. Fuel filter is 1 month old. Now It just drops hard without warning in idle or gear, high or low RPMs. Would appreciate any advice. TIA.

 

[Scott Danforth]

Sounds electrical.

 

[Rboucher111]

Yeah that's where I'm leaning. I'm pretty handy with a multimeter. Any idea where to start? I recall some kind of breaker box on top of the engine next to the left manifold.

 

[Scott Danforth]

Start with ignition circuit. Its the purple wire.

 

[RCSConstruction]

You're getting spark and fuel but it's not even coughing when trying to start?
That's a weird one.
My first thoughts were fuel pump or distributor/coil which could still be a possibility.. (weak spark or low fuel pressure)

 

[MariahZ220]

Sounds like my experience a few years ago with my 7.4L, mine turned out to be a bad diode in one of the wiring harness's. many hours spent trying to find the problem between myself and my boat mechanic.