Engine sputters when turned off

[boater4021]

Hi folks - first time poster. Have a 2005 Bayliner with a Mercruiser 4.3L turnkey start. Starts up pretty well, runs great, but when turning off it struggles to turn off all the way and just sputters for a bit. If I'm in idle for a while it turns off normally but after running on the lake for some time it really struggles. I've tried to research and it sounds like it could be carbon build up in the carburetor. Thought I'd ask here. I have a link here to a video where you can hear the noise (hopefully it's okay to link to a video). Would appreciate any help. I'm a weekender at best so it goes a little while at times without being ran and I'm still trying to learn how all this stuff works.

20240825_145241.mp4

drive.google.com

 

[Scott Danforth]

That is run on.

That little gasp at the end is the motor running backwards and sucking water from the exhaust

You either have the timing out of spec, are running hot, or are running too rich

 

[Bt Doctur]

if the engine temp is normal and timing is correct then your probably running lean, get the special too ,not that expensive and open the mixture screw a bit

 

[boater4021]

Thanks, I had been reading up on how to adjust the timing so will try to get that a try first then try to figure out running too hot or too lean. First I've heard of that.

Not sure what it meant by get the special?

 

[Scott06]

Thanks, I had been reading up on how to adjust the timing so will try to get that a try first then try to figure out running too hot or too lean. First I've heard of that.

Not sure what it meant by get the special?

Special tool was a typo. The idle mix screw on the TKS carb has an anti tamper screw so you don’t richen it and change emissions. you need a merc too, to alter it. Typically these were factory set lean as hell. Same thing happens with lawn equipment nit uncommon to fatten them up a bit.

 

[boater4021]

Ah, okay, thanks, I'll look into that tool.