1986 Johnson 40hp - Stalling at idle

[bluefightingcat]

So I bought a boat and it came with a 1986 Johnson 40hp (J40ELCDE). It worked fine when I bought it and when I tried it out several times in the drive. But now that it's on the water, as soon as I start it, it will run for a few seconds and stall. I have no problems starting it but it will not run at idle for more than a few seconds. I use the "hand throttle/fast idle" lever to start the engine and I never get a chance to put it down since it stalls before it even has a chance to warm up. When I manually open the carbs, the engine seems to run fine.

First I thought it was a leaking primer bulb that caused the issue, but I replaced that but it didn't help. Next I took off the air silencer so that I could see what's happening in the carbs.

When I manually open the carbs in order to keep the engine running I observed two things:

1. Top carb was spitting some fuel out from the front end
2. Lower carb was not really doing anything. I couldn't really see any sign of fuel anywhere.

First I thought that the top carb's reed valves are worn but when I had a look, all reed valves appear to be fine.
So now my theory is that the bottom carb is blocked up and is not providing any fuel.

Before all this happened I had checked the compressions, and both cyclinders were around 110.

What do you think? What could be the problem?

I plan to rebuild both carbs since they are out of the engine but any advice would be much appreciated.

 

[racerone]

I think the compression should be around 140+ PSI.----So perhaps test with another gauge.

 

[oldboat1]

Carbs should be pretty easy rebuilds. Buy a couple of oem kits with floats. Disassemble and soak tops and bottoms in solvent, then clean and flush each orifice (all small openings). Be sure to remove domed covers on top to open idle passages (replacement caps in kits). I leave the brass jets in place as they are easily damaged.