1998 Mercury 150 hp EFI running problems

[eric2d3d]

I have been trying to fix this issue all year long and am about to give up. Heres is the issue the boat runs a little rough at idle but starts up fine as soon as you give it throttle at about 2000 rpm it feels like the engine is running on 3 cyl it will do this until about 3400 rpm on plain. Sometimes it will not stop even when on plain. The engine does smoke quite a bit even when warm idling. It is just driving me crazy.

Parts that have been changed with new Parts

Replaced both switch packs
Trigger
Stator
Both voltage regs
Plugs BU8H
Wires
CCMS reeds
Injectors sent out to be cleaned and tested
Air bleed system was cleaned and new line installed
Electric fuel pump replaced
Fuel filters
Low pressure fuel pump rebuilt
TPS set to .250v
Fuel lines replaced
Timing set to 6 btdc idle and 20 atdc
Oil pump delete kit installed
Switched to pre mix use only mercury 2 cycle oil
Thermostats
Checked magnets on flywheel all seem in place and good


Compression is cyl #1 122psi, cyl 2 118psi, cyl 3 120psi, cyl 4 119psi, cyl 5 120psi, cyl 6 120psi

Spark tested good on all cyl at idle on muffs


Please HELP

 

[woody66912]

Make sure the map sensor hose that comes out of the back of the ECM fuel controller is not pinched. Thats the black box in the front. The hose will exit the starboard side of the ECM down low. just went though this this summer, sent it out to CDI for repair to no avail. the sad part of this is you can't plug in to see if that's the issue I ended up going off what merc service said. Send it to CDI. $1.800.00 later for the repair, well I and the customer got screwed. Forgot to say the hose is the intake for the Map sensor.

 

[Dukedog]

Its got an "idle timing stabilizer" module on it. Throw it in tha trash. Reset idle and max timing. Set idle timing in tha water, in gear (on tha trailer is fine) at whatever tha motor and you like (rpm). Idle timing only is what determines idle "speed". Set max at 23 degrees advance crankin' speed.........Its s start!

 

[eric2d3d]

I checked the hose that goes into the ECM it was connected and was tested for leaks.

I took the boat to the lake after removing the idle stabilizer and set base WOT timing to 23 degrees and set Idle timing to 5 degrees BTDC and same problem was there as soon as u gave it throttle to get on plane it felt like it was running on 3 cyl but as soon as it got on plane it smoothed out and ran good but as soon as u backed out of the throttle enough to just get off plane it would start running bad again like it was only running on 3 cyl.

I removed the pugs and found this the even side was light brown plugs and the odd side were all black I uploaded a pic of the plugs the lighter ones are even sid the darker plugs are odd side.

 

[Dukedog]

When checkin' tha tpi did you run tha throttle up n down? It should max out around 7 v. best I remember but must be smooth goin' up n down tha range. It only effects idle and mid range. Has no effect on wot......

Even with all tha new 'lectrics it still sounds like electrical problem. Might even be tha ecu. A little time involved but you can swap tha switch boxes, stator, trigger feeds ta see if problem follows with any of tha moves......

 

[eric2d3d]

I will switch the switch boxes around this week and re test it for a little while and see if the plug colors change sides also the tps should read .250 to 7v with the temp sensor unplugged correct I will check that tomorrow. I hope it is just a bad switch box or something cheap if it is an ecm I might be making this motor a carb motor. Also you say the tps doesn't effect wot then what should my voltage be reading at full throttle. Thanks

 

[Dukedog]

Think 7.5 max........

 

[eric2d3d]

TPS looks to be good idle was .249 and smooth climb to 7.47 volts will be swapping switch boxes around and testing this weekend. Is there any more test to run on the switch boxes or trigger i can run without the boat in the water. THANKS

 

[Dukedog]

Google "Outboard V6 EFI". Should be a pdf link on top "outboard v6 efi - river-service.ru"

That should open a technicians manual.......Let me know if it works.

 

[eric2d3d]

Thanks for the link should help me out some more thanks

 

[eric2d3d]

well switched the switch box around and the problem moved to the other bank. so I installed the good old switch box and now everything is running good. Also the engine is running rich from idle is there a way of adjusting it to run leaner. Thanks

 

[Faztbullet]

Also the engine is running rich from idle is there a way of adjusting it to run leaner. Thanks

Raise the idle timing and adjust throttle arm , to tell if rich running premix. On factory ECU there is no adjustments like aftermarket has...