88 Johnson bogging down

[thebottomfish]

Thanks for the ideas, timing arm looks like it's advancing, spark at all 4 cylinders, I'll have to check the fuel line at the valve good idea!
When you say the carbs are very delicate, what kind of solution should I soak them in? Or should I just clean with carb cleaner and blow them out with compressed air?
I guess I couldn't have messed up the timing by spinning the flywheel then right?