3.5hp 4 stroke Mariner. Stalling when accelerating from idle

[pikeman2210]

Hello, this my first post as new to this forum. I have a 2012 Mariner 3.5hp 4 stroke. Had it from new. Serviced it myself after the first dealer service. Had no issues with it until this summer. I had some old fuel in the tank (circa 6 months old) and thought I'd give it a go. engine didn't like it. So in the field I drained the tank and put fresh fuel in it. Ran ok but had acceleration issues from idle. Stalled if tried to accelerate too quickly. If accelerated slowly wasn't too bad. Once home I drained the tank and flushed out the carburettor. Undid what was undoable to clean the carb. Am I correct in that these carburettors are fixed, that is apart from idle revs are un-adjustable? First time out recently after the 'clean' the engine runs well except when accelerating hard from idle. I can run at full rpm then back off a bit then back to full without a problem but as soon as I go to idle and then turn the throttle to accelerate quickly the engine stalls. Starts up again first pull. If I turn the throttle slowly from idle the engine runs ok. Anyone any thoughts? Am I correct in my assumption of a non-adjustable carb? Regards Stephen

 

[racerone]

It is adjustable.----Remove cap of low speed mixture screw.-----Open 1/4 turn.----Test run.

 

[pikeman2210]

It is adjustable.----Remove cap of low speed mixture screw.-----Open 1/4 turn.----Test run.

U have lost me a little. I'll have to get back to you with photos of my carb so you could point out which screw. Be a while (4 weeks) as I have had an eye op and not to do any unnecessary bending or lifting. Regards Stephen

 

[QBhoy]

Hi. I had an identical engine and year.
These things are famous for needing their carb cleaned often. Especially after it was known for them to take oil back into the carb, even if they were stored on the correct side in storage. They just do it. Also the oil level is crucial to have correct too. Too much and the same happens. The carbs on them are pretty poorly made fragile things. Very easy for them to loose a seal or get gummed up easy. Can almost bet my life on it running ok, after a good carb clean. Dead easy to do.

 

[pikeman2210]

Hi. I had an identical engine and year.
These things are famous for needing their carb cleaned often. Especially after it was known for them to take oil back into the carb, even if they were stored on the correct side in storage. They just do it. Also the oil level is crucial to have correct too. Too much and the same happens. The carbs on them are pretty poorly made fragile things. Very easy for them to loose a seal or get gummed up easy. Can almost bet my life on it running ok, after a good carb clean. Dead easy to do.

Hello, I did dismantle it and clean it. It looked fine but cleaned it anyway. Still had the stall when idle to quick full throttle. Mine seems to be the type where the mixture setting is fixed. Mind you seen a You tube vid where the brass cover plate is drilled out to access the mixture screw. I'm planning to convert it to 5hp with a metal prop and 5hp carb at some point. Regards Stephen

 

[QBhoy]

Hello, I did dismantle it and clean it. It looked fine but cleaned it anyway. Still had the stall when idle to quick full throttle. Mine seems to be the type where the mixture setting is fixed. Mind you seen a You tube vid where the brass cover plate is drilled out to access the mixture screw. I'm planning to convert it to 5hp with a metal prop and 5hp carb at some point. Regards Stephen

Yeah. I had to mess with the mixture screw on mine. Had to access it first. I’d also politely suggest that my first and second attempt at cleaning the carb were just in the usual fashion by hand. After the same result…I used an ultrasonic cleaner. Perfect after this.

 

[pikeman2210]

Yeah. I had to mess with the mixture screw on mine. Had to access it first. I’d also politely suggest that my first and second attempt at cleaning the carb were just in the usual fashion by hand. After the same result…I used an ultrasonic cleaner. Perfect after this.

Well, being retired I no longer have access to an Ultrasonic cleaner. But I take your point. I can live with the fault just gets a little annoying after a while lol. Once I've got the all clear I'll give it another look. Regards Stephen

 

[QBhoy]

Well, being retired I no longer have access to an Ultrasonic cleaner. But I take your point. I can live with the fault just gets a little annoying after a while lol. Once I've got the all clear I'll give it another look. Regards Stephen

Worth getting into the mixture screw I’d say. Had to fine tune mine a little to get it to stop the bogging under acceleration on mine.