Re: 40 hp mariner sputtering in midrange
Moving from low speed jets to high speed, or timing. Doubt timing as you probably have the throttle at a constant position. Crud in the carb could cause it in my opinion.
Back in the '50's midrange variations were a common problem. You had adjustable low and high speed jets. Seems modern engines, with their fixed high speed jets have cured that problem. If you do a carb cleaning ensure that you shoot the jets and every hole you can find with compressed air. I found my problem in a high speed jet and would have never seen it had I not blown air into it.
Mark
