Re: 1999 90hp Johnson... stalling out
What you did was good preventive maintenance. Now, we get into some deeper diagnostics.
Are you running this on an inboard fuel tank? If so, does your primer bulb go flat when the engine acts up? If so, the anti siphon valve, on the outlet of the tank is sticking. Or, your fuel filter, if equipped, is clogged. Any marine store will have replacements, they are cheap. If that is not it, go to the next step below.
Do you have an inductive timing light? If not, borrow/rent one.
Once you have the light, put the inductive lead on each plug wire while the engine is acting up. This will tell you what cylinder is or is not firing. Once that is known, we can go further.