Logo
FULL SITE MENU

Firing issue

J

jonboy2542

Member
I have an 85 mercury 150 xr2 that isnt firing on one cylinder. It will fire if the rpms raise but not at idle. I have replaced the plugs, wires, and coils.

When i took the boat out a week ago it seemed fine at an idle but as soon as I put into gear, it shook and struggled to get on plane. The it would start going after 10 to 15 seconds but rpms would ho up and down some.

I also tried adjusting the timing some and it started firing at an idle. But i know my timing is off now. Hello me out please
 
Not sure why you would adjust the timing as it does not go out of adjustment on this motor.-------What other trouble shooting has been done?----Compression test numbers are ?----Did this problem develop suddenly ?
 
I didnt think adjusting the timing would have been an issue either, but someone had mentioned it to me so I decided to try it. As for compression, each cylinder is around 130 to 135 psi.

A few months back I replaced both power packs as they were bad. It has been running great since then, until 2 weeks ago. It cranks fine.
 
Swap the switchboxes and see if the problem moves.

You note they were both replaced but that doesn't rule out one going bad again.
 
How can it be the switchboxes? Since it sparks at high rpm, just no spark at idle unless I adjust the timing (which i know is off now).

I tested the spark with a spark plug tester. It lights up with spark. All other cylinders have spark.
 
jonboy2542 said:
How can it be the switchboxes? Since it sparks at high rpm, just no spark at idle unless I adjust the timing (which i know is off now).

I tested the spark with a spark plug tester. It lights up with spark. All other cylinders have spark.
Click to expand...

Adjusting the timing increases or decreases rpm. Seems that your issue is RPM related. Move the switch boxes and retest.
 
I switched the boxes and all cylinders were firing, then one cylinder barely had any spark and then non. Now its the opposite cylinder. So I guess i need new boxes again. What would cause them to go out within 6 months? And thanks for all the help
 
Ok thank you. It doesnt have the idle stabilizer on it. I ordered cdi boxes this time. Hopefully I can get it running right. I am trying to sale the boat soon
 
Back
Top