I have a I/O carb boat engine. sometimes it sputters when shut off. What could cause this?

Answer 1

Braking too quickly.

Answer 2

That sputter is called dieseling by most mechanics. There is an excess of carbon built up in the head area where the spark plugs are. It is usually an indication that you are using crap gas on that your timing is off, retarded too much. Determine whether or not you are using the right octane fuel, if so, get your timing checked. Setting the timing where it should be will not fix the problem right away, you still need to burn off the carbon. If you have a carburetor, it could be running to rich also. If this is a once and a while problem and doesn't happen for a long time frame, don't sweat it too much.
If you come from a fast speed and let the engine idle for a while and do a proper cool down, you are less likely to experience this.

Answer 3

It is called dieseling, but contrary to popular belief here, the main cause is the engine running too hot. What is actually happening is , there is gas in your cylinders when you cut the switch, that gas is compressed on the compression stroke and if the engine is hot enough it will ignite without the spark.

Higher octane gas will help, because it burns hotter and more completely, leaving less in the cylinder. Adjusting your timing will help by letting the plugs fire at the right time which in turn will give you a more complete burn and more power.

Keep an eye on that temp gage. If it's going over 190 it's definitely running too hot. Inboard/ outboards are famous for the exhaust risers corroding and getting blocked. That's where I'd start looking if it is running hot.

Answer 4

all I/O's need to run premium gas. the "sputter" is surely called dieseling and it's caused in boats by lesser octane gas. if your engine is pretty old, the timing may need adjusting. the newer ones have electronic control and actually setting the timing doesn't have much effect on "sputter".

Answer 5

If the motor vehicle is older, the spark plug cables get previous and improve nice cracks and reason this without showing up on diagnostics. If the nicely known motives are eradicated, i might replace the cables. vehicle might must be a minimum of seven years previous or in a warm dry climate. If that's greater in all danger to happen in damp climate, that's an extremely in all danger reason. If it happens when you get the motor vehicle good and warmed up, and happens each and every time you get it heat. Have them verify if there is moisture on your engine oil. that's not good through fact you have a block crack to the interior. quite some different motives, yet those are ones that i come across machanics pass over.

Answer 6

what do you mean sputters? Like it keeps running after you turn it off? That's usually improper timing, or carb. adjustments

Answer 7

Is your idle rpm over 650 than if not lower it. See if that takes care of the issue?Or your carb could be dripping gas into the manifold timing advanced to much.Something to think about. What is your temp? Close system anti freeze 162 open system 145.

Answer 8

Overheating or suspect head gasket.