2003 Mercury 150 starting problem

[ccsicc]

Hello fellow boaters! I am new with this forum but had browsed through threads similar to the issues I am having.

Outboard will not start in neutral. It will though in full throttle. This is the only way it can be started, give it a WOT, choke, and fire the engine. Problem exist even if the engine is warm. I tried warming up the engine, turn it off, and will never start in neutral. Engine runs fine in all speeds.

I replaced the plugs, fuel line and fuel filter/water separator as my initial troubleshooting step - It still have the same problem. I bought a Clymer manual and browsed for possible solution. One solution I stumbled is the shift interrupt switch. I will check it today when weather permits.

Any other thoughts will be greatly appreciated.

 

[hkeiner]

Re: 2003 Mercury 150 starting problem

When the motor is cold or warm, check for a good spark with a spark tester when the motor won't start in neutral. That will confirm that you do not have an ignition system problem.

You do not mention of the motor is flooding with a lot of smoke after failing to start in neutral and then starting the motor with the throttle at WOT. I ask because perhaps your starting procedure can be improved:

When starting cold, you have to hold the choke in for 5-10 seconds to adequately richen the fuel mixture in the carbs. If you only hold the choke in for a brief 1-2 seconds, that will make cold starting much harder. As you may know, there is no choke plate in the carb throats. The choke button opens an Enrichener Valve that allows extra fuel to flow into the bottom four carb throats while the button is being pushed in.

When starting warm, you should not choke at all and you do need to push the throttle lever a bit forward of neutral. If you keep the throttle lever in the neutral position, the throttle plate is fully closed and that can cause flooding and hard starting because very little air is getting to the cylinders. Opening the throttle plates a little give the cylinders more air. You do not need to push the throttle all the way to WOT, but setting the throttle for a fast idle (1000 rpms or so) should do it.

There is also a Thermal Relief Valve that controls air flow into the carb's low idle circuit. The valve is mounted near the back of the motor and an air hose goes from the valve to the carbs. The valve is closed when the motor is cold and opens when the motor is warmed up. If this valve is not working correctly (stuck open or stuck closed) it can cause starting problems too.

Of course, other typical suspects include a clogged fuel filter, a bad link and sync setting, incorrectly adjusted floats in the carbs, dirty carbs, and other maintenance related causes.