Haha, oh yesss.. the notorious electric fuel pumps. I have Two 4.3 EFI Volvo Penta's in my 278 Vista, and lets just put it this way - I keep a spare Low & High pressure fuel pump ON BOARD at all times. Yes, they can (I would say 90% of the time) whine before they go bad. When they go bad, they usually don't fail completely; if your engine stalls, or wont go above xxxx RPMs, you can usually "tap" the fuel pump with the handle of a screwdriver real good a few times, or some other blunt object, and it will clear it up temporarily. Fun fact: If you change the fuel pumps, you WILL need new O-rings. The old O-rings almost always get shredded after removing the pumps (by design maybe?).
By the way, the first few times I purchased Volvo Penta OEM pumps...BIG$ mi$take. They still go bad eventually too, there is nothing magical or special about them, except their price. VP doesn't make the pumps, they are Carter pumps. I cross referenced the VP pump to Carter, and went from paying $200 each to $40. Heck, once on Amazon, they were clearancing the Carter pumps out for... get this.... $18!!!! I bought a few that time. One in the boat as a spare, and the rest go in my heated dry garage as spares.
Now remember, I have FOUR pumps; 2 high and 2 low (I have Twin engines). I find that at least 1 of the pumps goes bad about every 3/4 years. They just don't last. But I am well versed now to know when one IS starting to go bad. And like you posted about, whining is the first sign. Hard starting, stumbling when getting on plane, RPM's bouncing (starts out minor) on plane.
Maybe this will help someone who reads this in the future, but here are the cross reference part numbers from VP to Carter. This will save someone a SUBSTANTIAL amount of money. You're Welcome
Remember, you will want to replace the O-rings on each end of the fuel pumps when replacing the pumps!! I bring mine into my local NAPA and get them. Make sure you get the ones that are rated for use with fuel (they are usually brown colored IIRC).
If you need VP 3854620 (Low Pressure)... then you want Carter P61122, or Airtex E8264
If you need VP 3854280 (High Pressure)... then you want Carter P61171, or Airtex E8266
Right now on Amazon, the E8266 is $29! And the E8264 is $91. A far, far FAR cry from dealer or Volvo Penta prices when the pumps ARENT made by VP anyways. Total racket.