Crusader CH220 (305 Block) bogging at high rpm and burning way more fuel

Hoping this community can help me out.

I have twin Crusader 220's on my 1965 Shepherd Cruiser. We bought her last Fall. Port engine runs fine and uses 60% of the fuel that the starboard engine burns. At WOT I'm supposed to get 4000 RPM. Port seems like it could get there no problem (had it at 3600 with room to go on throttle) but starboard starts getting bogged down around 2500 and will only get to 3000. Once there it swings between 2600 and 3000.

A few things I'vr checked so far:
- swapped carbs made no difference to bad engine.
- set timing and confirmed mechanical advance works properly
- pulled #1 plug and it was quite black.
- new fuel lines, water separating filters and carb filters
- vacuum is lower on bad engine, 15 at idle 10 under load (2000 rpm). Good engine is 18/15.
- checked intake manifold and carb for leaks with ignition spray and brake cleaner. No revving occurred.
- cleaned contacts in distributor. Both distributors had some build up. Also put new mechanial advance springs in.
- compression test done in Oct, all cylinders looked good.
I don't think it's fuel supply related as the bad engine is burning so much more fiel and swapping carbs made no difference. It could be a prop issue but both are marked 16x14. I have a spare set of 16x14 that had balanced and checked that I would like to get on to be sure but I think the props are ok.

I should add in Mar I ran both engines at around 3600 rpm no problem. Just one time though. We have since made some friends in the wooden boat community and were surprised to hear they were all cruising at 18-22 knots and burning 2 Liters per nautical mile to our 4.5 at 8.5 knots. I wanted to see what our fuel burn was like up on plane.

My next steps were going to be new plugs, cables and swapping coils. Any help is appreciated, this i all new to me.
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I should add these engines are mid 80's crusaders

new to you last fall - did you get any maintenance records?

Did you verify the timing advance was correct After the new springs went into the distributor?

Changing the secondary side of the ignition would be a reasonable next step, especially since swapping carbs had no effect.

Any idea hour many hours are on the engines?

No maintenance records. Previous owner died and records on boat seem to predate him. He had an issue where that engine was overheating but he got it resolved. I've never had that problem.

Yes verified timing after replacing springs.

Going to swap cables and plugs today. Possibly replace ignition coil too if I can get another.

Hard to say, engine hr dials are original and these engines aren't. They say 2700 hrs but I don't think they have that many hrs. Risers and exhaust manifolds are all new and heat exchangers are 1 new and 1 in good condition.

understand...if the I'd add the distributor cap and rotor to the wires and plugs...

if the issue is still present, I'd suggest a leakdown test (or a compression test at a minimum)...

So I pulled all the plugs and replaced with new. All of the plugs had a .030" gap and Pertronix recommeds going larger by up to .007". The factory gap setting is .035".

The plugs were in pretty good shape but 3 or 4 looked wet indicating incomplete combustion. Which might explain the excessive fuel burn.

I also replaced all the cables and put on a new dist cap and rotor. Haven't had a chance to test under load yet, hopefully tomorrow. I'm going to check for an intake manifold leak again. The engine just sounds like it has to work harder than it's twin once we get to 2000 RPM.

Also swapped ignition coils just to rule that out

so how much timing advance do you see and what RPM is MAX timing seen?

Its somewhat hard to tell what the max numbers are brcause my harmonic balancer has an indicator mounted to the block that shows 0 and then 8 degress in the retarded direction and 12 in the advanced direction. I have both engines set to the advanced 10 at idle which is factory spec. Both engines have the silver springs in them which don't hit full advance until 3500 RPM of 24 degrees which makes for 34 degrees total. The mark on the harmonic balancer looks to be in that range.

I should add I only have trouble getting the rpms up under load. It's fine in neutral.

sounds like its not an advance issue...if you want an accurate reading of the timing, get a 'timing tape' or you can scribe the balance using a protractor...

Sounds like another run under load is the next step...fingers crossed...