Mercury 150-HP OptiMax: Hard Start, Rough Idle

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Author Topic:   Mercury 150-HP OptiMax: Hard Start, Rough Idle

easygoing_60565_guy664 posted 08-05-2009 07:28 PM ET (US)
I bought [a Mercury OptiMax 150-HP outboard motor] used and have had [problems with hard starting and rough idle] from day one. I have taken in to a shop where they fixed the problem, but it reappeared a week or so later. The plugs are one-year-old and the fuel filter has been changed along with the fuel line. The motor now seems to be running at three-quarter power. Recently, I added Seafoam to the fuel, which may or may not have helped the motor. But the starting and idle problem still is there. Any suggestions would be appreciated. Thanks. I'm new here, but signed up after seeing some dialogue on [Mercury OptiMax].
bluewaterpirate posted 08-05-2009 07:30 PM ET (US)
Did you pull the plugs and inspect them?
jimh posted 08-05-2009 07:40 PM ET (US)
Your Mercury OptiMax motor is an extremely complicated engine. It has 12 electronic injectors, an air compressors, dual fuel pumps, a high pressure fuel rail, a high pressure air rail, all sorts of valves, regulators, and plenty of hoses. It is really difficult to make seat-of-the-pants diagnosis of running problems. The engine is controlled by a sophisticated computer control system which can be used to help make diagnosis. You need to find a Mercury certified OptiMax repair technician who has all of the very specialized hardware and software needed to work on that motor. Let him connect to your motor and read the diagnostic codes.
sosmerc posted 08-05-2009 10:09 PM ET (US)
I secondJimhs thoughts.......Complex engines...but still the basics apply......you need good compression, good fuel, and good spark.
The Optimax is a standard 2 stroke...but the external systems are a new design...and you need the proper diagnostic equipment and service manuals to properly repair.
L H G posted 08-05-2009 10:21 PM ET (US)
Take it to Berwyn Marine, on Ogden in Cicero. They'll fix it up for you. Is it one of the early Opti's?
easygoing_60565_guy664 posted 08-06-2009 07:43 AM ET (US)
I fialed to mention that after running the motor at cruising speed or top-end, the throttle won't let me into neutral, but when it does or if I turn off the motor, put it neutral, then restart, the throttle is revving the motor at more than 5000 rpm. At that point, I can only turn it off to stop the revving.
It must be an older Optimax model. I say that because the serial number is supposed to be on the left or right side of the mount on the stern, but could only find a number in the area between the motor and its swivel point. It is 826431-C. I entered that into Mercurymarine website and it kicked it out saying to check with a local repair shop. This suggests it is pre-2000. I'm trying to save money with a self repair, but it sounds a bit more complicated than I thought.
easygoing_60565_guy664 posted 08-06-2009 08:07 AM ET (US)
I had an opportunity to speak with a mercury repair shop guy. Without hooking it up to the diagnosic computer, he suggested I look into changing the throttle sensor, first and changing the air intake valve, second. I think he said the sensor is located by the controls in the cockpit? I am correct in the sensor location?
jimh posted 08-06-2009 09:19 AM ET (US)
In any motor with electrically controlled fuel injection, there typically is a throttle position sensor which provides an electrical signal that varies in proportion to the throttle plate position. The sensor is mechanically linked to the throttle plate. Locate the throttle plate linkage on your Mercury 150-HP OptiMax motor, and follow the linkage to the throttle position sensor.
The throttle position sensor (TPS) is typically just a variable resistor. The resistor is supplied with a voltage, and the wiper arm of the variable resistor returns a variable voltage proportionate to the throttle plate position.
Problems with the TPS can be either mechanical or electrical. If the linkage is misadjusted, loose, or slipping, the input shaft of the TPS will no longer correspond with the throttle plate position, causing the engine's controller to become confused. If the variable resistor has deteriorated, or if the wiring to the TPS is is damaged, or if the voltage supplied to the TPS is erratic, the electrical signal being generated will no longer correspond to the throttle plate position and the engine's controller will be confused.
aussiejake posted 08-08-2009 04:43 PM ET (US)
If the throttle position sensors are malfunctioning the early optimax motors had a continuous audible alarm go off. If you do not hear this whilst the motot is running dont waste your money on a new sensor. Also the early optimax motors had 2 throttle position sensors.
As suggested by others have it diagnosed properly before spending and wasting $$$.
easygoing_60565_guy664 posted 08-14-2009 10:49 PM ET (US)
Thanks for the help from all of you. If any other thoughts come to mind, do not hesitate to post a reply. Thanks again.

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Author	Topic: Mercury 150-HP OptiMax: Hard Start, Rough Idle
easygoing_60565_guy664	posted 08-05-2009 07:28 PM ET (US) I bought [a Mercury OptiMax 150-HP outboard motor] used and have had [problems with hard starting and rough idle] from day one. I have taken in to a shop where they fixed the problem, but it reappeared a week or so later. The plugs are one-year-old and the fuel filter has been changed along with the fuel line. The motor now seems to be running at three-quarter power. Recently, I added Seafoam to the fuel, which may or may not have helped the motor. But the starting and idle problem still is there. Any suggestions would be appreciated. Thanks. I'm new here, but signed up after seeing some dialogue on [Mercury OptiMax].
bluewaterpirate	posted 08-05-2009 07:30 PM ET (US) Did you pull the plugs and inspect them?
jimh	posted 08-05-2009 07:40 PM ET (US) Your Mercury OptiMax motor is an extremely complicated engine. It has 12 electronic injectors, an air compressors, dual fuel pumps, a high pressure fuel rail, a high pressure air rail, all sorts of valves, regulators, and plenty of hoses. It is really difficult to make seat-of-the-pants diagnosis of running problems. The engine is controlled by a sophisticated computer control system which can be used to help make diagnosis. You need to find a Mercury certified OptiMax repair technician who has all of the very specialized hardware and software needed to work on that motor. Let him connect to your motor and read the diagnostic codes.
sosmerc	posted 08-05-2009 10:09 PM ET (US) I secondJimhs thoughts.......Complex engines...but still the basics apply......you need good compression, good fuel, and good spark. The Optimax is a standard 2 stroke...but the external systems are a new design...and you need the proper diagnostic equipment and service manuals to properly repair.
L H G	posted 08-05-2009 10:21 PM ET (US) Take it to Berwyn Marine, on Ogden in Cicero. They'll fix it up for you. Is it one of the early Opti's?
easygoing_60565_guy664	posted 08-06-2009 07:43 AM ET (US) I fialed to mention that after running the motor at cruising speed or top-end, the throttle won't let me into neutral, but when it does or if I turn off the motor, put it neutral, then restart, the throttle is revving the motor at more than 5000 rpm. At that point, I can only turn it off to stop the revving. It must be an older Optimax model. I say that because the serial number is supposed to be on the left or right side of the mount on the stern, but could only find a number in the area between the motor and its swivel point. It is 826431-C. I entered that into Mercurymarine website and it kicked it out saying to check with a local repair shop. This suggests it is pre-2000. I'm trying to save money with a self repair, but it sounds a bit more complicated than I thought.
easygoing_60565_guy664	posted 08-06-2009 08:07 AM ET (US) I had an opportunity to speak with a mercury repair shop guy. Without hooking it up to the diagnosic computer, he suggested I look into changing the throttle sensor, first and changing the air intake valve, second. I think he said the sensor is located by the controls in the cockpit? I am correct in the sensor location?
jimh	posted 08-06-2009 09:19 AM ET (US) In any motor with electrically controlled fuel injection, there typically is a throttle position sensor which provides an electrical signal that varies in proportion to the throttle plate position. The sensor is mechanically linked to the throttle plate. Locate the throttle plate linkage on your Mercury 150-HP OptiMax motor, and follow the linkage to the throttle position sensor. The throttle position sensor (TPS) is typically just a variable resistor. The resistor is supplied with a voltage, and the wiper arm of the variable resistor returns a variable voltage proportionate to the throttle plate position. Problems with the TPS can be either mechanical or electrical. If the linkage is misadjusted, loose, or slipping, the input shaft of the TPS will no longer correspond with the throttle plate position, causing the engine's controller to become confused. If the variable resistor has deteriorated, or if the wiring to the TPS is is damaged, or if the voltage supplied to the TPS is erratic, the electrical signal being generated will no longer correspond to the throttle plate position and the engine's controller will be confused.
aussiejake	posted 08-08-2009 04:43 PM ET (US) If the throttle position sensors are malfunctioning the early optimax motors had a continuous audible alarm go off. If you do not hear this whilst the motot is running dont waste your money on a new sensor. Also the early optimax motors had 2 throttle position sensors. As suggested by others have it diagnosed properly before spending and wasting $$$.
easygoing_60565_guy664	posted 08-14-2009 10:49 PM ET (US) Thanks for the help from all of you. If any other thoughts come to mind, do not hesitate to post a reply. Thanks again.