Issue with 35hp Mercury outboard

I’m looking for your help with diagnosing a problem I had last night with my outboard. I ran it for about 20 minutes last night, at a slow idle for about the first 10, then probably 3/4 throttle for 5 minutes, then back to an idle far about 5 minutes until it stalled out. When it stalled out it seemed like it ran out of fuel, or wasn’t getting fire. When I increased the idle it would eventually start but kill as soon as I dropped the idle and tried to put it in gear. The boat has not been ran much over the past few years, I changed the lower unit oil, put fresh gas in it, and topped off the oil, which has a seperate tank that mixes on the way to the motor. The gas tank vent was open. Any thoughts? I plan to change the plug today, would cleaning the carbs be the next logical step?

Thanks,

Matt

yeah that is the logical step. if an outboard runs lean, it doesn’t just quit, it runs, coughs, runs, coughs and then dies. all it takes to mess it up is a tiny speck of rust in the carb.

Trade it in for a Johnson/Evinrude after you clean your carbs, yes..

Same thing happened today. It started after many attempts, ran rough for awhile, but eventually started running fairly well at low speeds for 20 minutes or so. After running pretty much full throttle for a few minutes and then back to an idle it stalled out again after a few minutes. I’m getting plugs tomorrow.