1989 120hp wont idle without linkage adjustment

[countvlad]

I've always had idle issues with this engine. A friend of mine, few eyers ago, tuned and adjusted the idle but it was always done through the linkage adjustment, where you turn the linkage stop to open up the carbs butterflies.

I've tried to do the link and sync per factory manual (I own one) but the engine just dies or idle really erratic.

Over the winter I've rebuild the powerhead. My thought was that the idle will be back to normal where i can do the link and sinc per manual. We'll thats not the case. I still have to adjust the linkage where the butterflies are slightly open in order to keep the engine idling. Currently its idling anywhere between 700-850 in gear in the water.

It seems to me that the engine is choking for air, as though it needs air to run. I've changed the idle bleeds from 41 to 35 and 27, but with no success. Next, I was thinking of going up to 50, since i have some laying around.

Troubleshooting I've done so far:
New coils, wires and spark plugs - Checked for spark 7/16 on all cyl they looked good
Compressing was 120 on all cyl
Checked the stator and trigger points - All good
New rectifier
Carbs rebuild
I have clear hoses between fuel manifold and carbs and there are no air leaks
Recirc valves are cleaned and fairly new.
Thermostats open and heads temp around 160
fresh gas

Any advice ideas on why i have to have the carb buterflies slightly open to keep the engine idling?

Thank you

 

[CBOATNAZ]

I recently rebuilt some carbs for a 135, and I did a flow test of the low idle circuit to prove there was no blockage. If you remove the Welch plugs inside the bowl area you can clean them out with small wires poking through the holes. I did not remove the Welch plugs, so I opted to plumb a water supply to a 1/4-28 bolt (with a hole drilled through it) and thread it into the low idle jet hole and verify good flow through the holes in the venturi area. I used a piece of rubber to block the port into the bowl. This forced the water out the idle circuit. If you had and build up or dirt problems, this might be a place to look.

 

[countvlad]

I did clean the throttle body holes with carb cleaner before installing it. All four holes had a nice cleaner jet coming out.