Dieseling 3.0

[cbummy]

My 2010 bayliner 175 has started dieseling pretty bad. When I reach a spot I want to shut the motor off I have to let it idle form quit awhile before shutting it off. Has anybody had luck with the seamfoam spray in cleaber?

 

[Jmunk]

I’m not sure a spray in cleaner will help. Might want to try using gas with a higher octane rating.

 

[airshot]

Watch your engine temps, check your gages to see if they read correctly. Often run-on comes with high cylinder temps. You might run a compression check also, as worn valves can cause this as well. A good carb cleaner won't cure your issue, but it wouldn' t hurt either.

 

[cbummy]

Watch your engine temps, check your gages to see if they read correctly. Often run-on comes with high cylinder temps. You might run a compression check also, as worn valves can cause this as well. A good carb cleaner won't cure your issue, but it wouldn' t hurt either.

I researched it and seems carbon build up on the pistons is the most common cause, atleast that's what I have been reading. Kind of makes since since it a carbureted engine and it can still suck fuel when thr engine is shut off. I am thinking maybe the cleaner you spray in let it hot treat then burn it off may help. It claims to clean carbon from the combustion chamber.
The motor runs great when driving!

 

[airshot]

Seafoam won't hurt anything, according to the mfgr they almost flood the engine with it until it stalls, then let it set......after 10-15 minutes run it with a rich mixture of seafoam in the fuel. Often a small external tank is used for this. When it fires back up, it will smoke like crazy!!
Often had people wonder if my motor was on fire !! But it did clean out the excess carbon and crud. Primarily used on 2 stroke engines, but can be used on 4 strokes. Do you run at slow idle speeds for long periods of time? This will cause excess carbon buildup internally.

 

[cbummy]

Seafoam won't hurt anything, according to the mfgr they almost flood the engine with it until it stalls, then let it set......after 10-15 minutes run it with a rich mixture of seafoam in the fuel. Often a small external tank is used for this. When it fires back up, it will smoke like crazy!!
Often had people wonder if my motor was on fire !! But it did clean out the excess carbon and crud. Primarily used on 2 stroke engines, but can be used on 4 strokes. Do you run at slow idle speeds for long periods of time? This will cause excess carbon buildup internally.

I usually only run at idle seep in no wake zones. When running the engine runs great.

 

[Scott Danforth]

Check your timing
Check the impeller
De Carbon the motor
Go thru the carb

If you run rich, and get carbon buildup, it will run-on. Running hot will also cause run-on

3.0's are more susceptible than the other motors

My 3.0 would diesel during watersports if you chopped the throttle right after a holeshot (skier fall, etc). I used to shut off in gear to prevent run-on

 

[nola mike]

I usually only run at idle seep in no wake zones. When running the engine runs great.

Also check your idle speed. Too high will make it run on as well.

 

[cbummy]

Check your timing
Check the impeller
De Carbon the motor
Go thru the carb

If you run rich, and get carbon buildup, it will run-on. Running hot will also cause run-on

3.0's are more susceptible than the other motors

My 3.0 would diesel during watersports if you chopped the throttle right after a holeshot (skier fall, etc). I used to shut off in gear to prevent run-on

Its not running hot the average motor temp is just above 175 the needle is just to the right of the 175 mark but still touching the line and stays there for the most part
Idle is around 500 if I remember right

 

[Scott06]

Its not running hot the average motor temp is just above 175 the needle is just to the right of the 175 mark but still touching the line and stays there for the most part
Idle is around 500 if I remember right

I used seafoam dribbled down the carb eventually stalling the engine, let it soak in 15 min , then run the engine and burn it off. This did help the dieseling. Merc also makes an aerosol called power tune to do similar

 

[Bt Doctur]

and it can still suck fuel when thr engine is shut off. NOPE
A hot rod trick is to run at a high idle and pour a coke soda bottle of water down the carb slowly. .It will vaporize any carbon in the cylinders.
The motor should have a 140 stat and never go above 160.
As per the other suggestions there are all valid causes for your issues