Re: 2000 mercury 150 rough idle
You probably need to do some basic troubleshooting and provide more information to get helpful responses. Hard starting and rough idle can be caused by a lot of things.
First check for good compression and good spark. I also suggest that you describe your starting procedure to see if it is the possible cause. On my 150hp, I push the throttle a little forward when starting it warm. This gives the motor a little extra air so that it does not flood so easily. You might also describe what the motor does when it finally does start. If it smokes a lot, that would guide you to one set of possible causes and if it does not smoke, another set of possible causes. Rough idle could be solved by a tune-up or carb rebuild.
These general thoughts might get you started, but the more troubleshooting info you provide the more helpful the answers will likely be.
Here is a laundry list of possible causes for poor idle, in no particular order.
- Improperly mixed fuel.
- Contaminants in fuel.
- Fuel tank air vent closed or restricted.
- Pinched, cut or restricted fuel line.
- Loose fuel line connection.
- A dirty or restricted fuel filter.
- Low fuel pump pressure.
- An anti-siphon valve.
- Needle and seat (in carburetor) that is either stuck open or closed.
- Improper carburetor jets, restricted jet or idle mixture screw out of adjustment.
- Improper carburetor float level
- Reed block housing loose, or gaskets are defective.
- Improperly routed or restricted bleed hose(s)
- Thermal relief valve stuck closed: Over rich at idle.
Good luck.
