My 9.9 Honda has seldom given me any trouble starting or running. That has changed this year, immediately after the annual full servicing. Hard to start, and if it fails to start, have to wait 20 minutes before trying again. Once running, no problem.
After several visits by the mechanics, who were baffled (no water in fuel, tank very clean, cooling water running well, fuel line bulb firm, seems to be a spark, it always started for them etc) I analysed that they might have made some small change in the carb settings during servicing but I continued with my customary start-up choke method and that would now cause flooding.
Got the mechanic to time and describe his method: throttle to start position, choke open for 3 seconds, then regulate revs with throttle until idling. I may have been keeping the choke open too long.
This worked for me for three separate times over a three-day period, then on the fourth start-up, back to apparent flooding, wait until no longer flooded etc. Also, coming back from sailing the other day she started easily under the new method, ran properly for 7 or 8 minutes, then quit suddenly (sails down in the harbour mouth, current flowing etc.) A short time later it restarted and brought us back to the slip.
Difficulty in starting, and sudden quitting, are both be problematic if not dangerous. Does anyone have any suggestions? Friends wonder if there is a thermostat that cuts the engine if the cooling water is blocked, which might explain the quitting, but I don't know if this era of motors would have that. Appreciate any ideas or advice.