slow to start, stalls w/ deceleration, air in lines
Hello, I have twin 3208 N/A engines and one of them now stalls when i decelerate but only after it's been running a while. This is the same engine that had a piston head break last year, followed by a new water pump. I also replaced the throttle shaft seal last year and have not had problems with that since. It was doing great for 50-60 hours after replacing the piston, including starting up without issues, but over the summer it stalled when backed all the way off the throttle while getting ready to anchor, after running smooth for the past 5 hours. Since then, this is what happens:
when it's hot, I have to bleed the lines, restart, and it runs in gear and neutral. I can accelerate and it will run, but as soon as I back off, it stalls.
If it's cold, it starts (after bleeding). In neutral, it runs fine while docked, whether I give it throttle or not. It's not until after it's been going a while that it stalls with deceleration.
I have checked all the lines and can't find anything needing tightened or obvious where air is getting in. I have not seen any evidence of a fuel leak when it happens. Before I had to replace the throttle shaft seal, I could get away with only bleeding the easily-accessible lines and the bleeder on top before starting, now I have to bleed both sides (I don't know if this matters or not...). Sometimes it cranks for a while before getting going, which I've seen asked several times in similar posts I've researched, but I'm not sure of the significance. From what I can piece together, I'm getting air from somewhere, but only with deceleration and only after it's been running a while. Possibilities might be lift pump, fuel pump, solenoid, or a loose line I missed. But if it was a loose line, wouldn't it always get air and run rough or stall?
I always seem to have some white smoke (not steam) with this engine. This winter I'm going to probably do as much as an overhaul as I can, hopefully it doesn't involve removing any pistons again! Until then, I 'd like to try to fix this if it's something I can diagnose or rule out easily, and if I have to address something really major, do it when I tear the engine apart in a few months. Any help is greatly appreciated, thank you,