Sorry for the delay. Wasn't able to test the motor until this past weekend. The TLDR is that the motor is working better than ever now!
Based upon the behavior, my theory was that it was starved of fuel at idle, then suddenly drowning when it transitioned onto throttle. Idle circuit was the main suspect, and I found that idle speed was too low as well at about 400 rpm. It's much happier now, running no-wake initial throttle engagement at about 550-600.
THE BATTLE: So... I DID get the fuel metering deck off...FINALLY. Soaked it with penetrating oil for days, then tapped it with a hammer enough to get a slight crack to open (tapping at the corners where it's strongest), then inserted a knife into the tiny crack which eventually opened and worked it back and forth while slightly prying. Took it slow and gentle and it finally came apart without any damage. Note: Holley paints the carb after it's assembled, and you can't get all the way around the metering deck to scrap the paint off. Once apart, the gasket stuck solid to both sides. In effect, to remove the deck, the gasket had to be ripped in half. (See pic). Seems like the gasket might have been glued on to both sides? Then again, 30 years of use without disassembly prolly didn't help!
Cleaning the old gaskets off both the fuel bowl and the metering deck was the most challenging and time consuming part. Maybe 4-6 hours in total? After much experimentation, the most successful method involved carb and throttle cleaner repeatedly sprayed onto gaskets, then using a plastic scraper for bulk work. Here, a plastic construction shim worked amazingly well and was totally resistant to the solvent. Then I chased down all the flecks of crap still adhered to each plate with the side of a bent dental pick, being careful to not scratch the surfaces.
As for discoveries related to my problem, it's clear that water had gotten into the carb at some point, causing oxidation in some areas. I pulled the idle jets, thinking the screws were clogged, but they looked fine. HOWEVER, when I sprayed carb cleaner and brake cleaner up the idle circuits above them (from fuel bowl to carb) neither responded well and one was pretty badly clogged. I then took a thin guitar string that I use to clean 3D printer nozzles and gently ran it down each circuit, twisting all the time while spraying the crap out of the circuits. I did this until I got a steady stream from both. Honestly, I suspect this was the biggest part of the problem.
Also, a surprising amount of carbonized soot had built up in the carb (which suggests a rich condition at some throttle position at some time in the past thirty years!). Cleaned all that off to get smooth atomization of fuel.
Fuel Mixture Screws: These were set to 0.9 turns out. That seemed too lean to me. Most tuning info on YouTube suggested 1.25 out as a starting place (which is richer). Did not have a chance to hookup a vacuum gauge when it was running to really fine tune the screws, but just by listening to the motor rise and fall as they were tweaked, 1.25 out seems dang good, if not spot on.
Power Valve: While I bought a full carb rebuild kit, ultimately I decided to not replace most items as I was afraid to change too many variables and screw multiple things up through ignorance. Really, I just wanted to clean the carb circuits and replace gaskets as a start. The Power Valve Jet was a #35 and had a little rust on it due to water infiltration. I figured this seemed too lean and since the carb kit came with a #45, I popped it in. I also twisted the house two hatch marks to in the richer direction, largely because the choke plate wasn't closing fully. I simply twisted it until the plate closed.
As there was evidence of fuel in the water (at a time unknown), I replaced the fuel/water separator. Dumped it into a glass, but saw no water. Replaced it anyway. Put it all back together, using gasket seal between motor and carb. Put 14 gallons of ethanol free gas in it, then tested her out.
Took a bit of pumping with key on to get the gas back into the fuel/water separator and to fill the fuel bowl, but as soon as it fired, it caught and idled well, if too low. Adjusted the idle screw once it warmed up to 550-600 and it purred like a kitten. Took her out after a long no-wake run without issue and once on open water opened it up. The damn thing jumped like never before! No issues from idle to throttle. Giving it full throttle from near idle was flawless and it came on-plane WAY faster than ever before.
I may tweak this for optimization at some point, but, frankly, I want to just enjoy the water for a bit and learn from it. I like the following suggestion from Zinister and may give it a try at some point in the future (yes, my cam is red):
Also a couple of other tips and things that helped me:
• I went one step stiffer on the Holley vacuum secondary spring. If you don’t already have one, I’d recommend buying Holley’s Vacuum Secondary Spring Kit. And While you’re at it, get the ‘Quick Change Secondary Spring/Diaphragm Cover’. That is worth every penny—it makes fine tuning the carb so much easier.
• I did swap out my accelerator pumps plastic ‘cam’ from a red color (or possibly could have been pink) to the dark blue cam. That moved more of the pump shot squirt towards the beginning of the throttle movement, which really helped eliminate the off-idle bog.
Really appreciate all the help from everyone and glad to report a successful outcome thus far!
