Dies throttling down

[Austinblake603]

I have a 2001 sea ray bow rider 185. Mercruiser 4.3 motor.

Dies throttling down
Lugs for a minute or two when the key gets turned off
Sometimes jerky throttling up.
Otherwise runs great.
What might cause this?
Thanks !

 

[itsathepete]

Lugs for a minute or two when the key gets turned off

Is it dieseling? Does it act like this

If you can, get the serial number off the engine. If not, at least let us know what you have. Carb or EFI. If EFI throttle body or MPI?

 

[Austinblake603]

Yes it diesels. And yes it’s carbureted.

 

[itsathepete]

Dieseling can be fuel, ignition, or carbon buildup. Start with ignition system. If you don't know how old the components are, replace them. Pull and inspect spark plugs. If they are carboned up, clean or replace them. Inspect the wires for damage or cracks, if they are damaged, replace them. Remove distributor cap and rotor. Look for carbon arc trails and burned contacts. Clean or replace if necessary. Check and reset ignition timing.
Now to the fuel system. Make sure fuel lines are in good shape. Replace fuel filter if not done recently. Remove fuel filter and dump contents onto paper towel in a bowl. Look for debris or water. Carburetor is likely somewhat dirty. Use a fuel system treatment (I like seafoam). Put cleaner in gas tank and run it. If it doesn't help, pull carburetor and clean/rebuild as necessary. If you use seafoam, it will help clean carbon off the intake valves which can help too

 

[Rick Stephens]

Other than the mechanic in a can, I agree with itsathepete. I would just assume the need to rebuild/clean the carburetor. Check timing and plug codition.

You must fix the dieseling. The last bit when an engine diesels it will run backwards. In a boat it will suck water in from the exhaust and damage your motor. Carbon deposits on the pistons getting hot will ignite the fuel despite ignition off, just like a glow plug in a model airplane.

 

[QBhoy]

Water in fuel and or carb needing cleaned

 

[Austinblake603]

Gentlemen thank you for the tips! I was thinking carb to start so thank you for the confirmation