Misfiring Suzuki outboard DF 70 4 strokes

[philoudent]

Hello everybody, I'm new on this forum and i hope you can help me with my engine problem

.

I took a video, the sound isn't perfect but you can see what happens


https://youtu.be/7QJgCbctHsU

Misfiring starts at 5 minutes running, no matter the engine rpm. they stop when i slow down at 3000 rpm. There is none alarm

The motor is a second hand, built in 2008.

Trying to fix it we :
- did computer diagnosis ( no failure)
-changed all filters (oil, air, water separator)
- put additives in fuel like water remover and injectors cleaner
- cleaned fuel injection rail and injectors manually
- controlled high pressure fuel filter

Despite it none amelioration
Does anyone has an idea ? We're trying to think to everything, temperature, pressure, electricity, defective part ... Our local mechanic is thinking about a bad contact in the vapor separator tank. We're waiting for a new cable ....

Thanks for your help

 

[99yam40]

have you tested to make sure the alarm system works?
Could be it is overheating and going into RPM reduction after 5 min


I have no idea how you controlled high pressure fuel filter
and I do not know what amelioration means

 

[clanton]

Check the shift switch. If out of adjustment, will limit rpms to app 3000. Check fuel pressure at 3000 rpms, should be 46 lbs.

 

[philoudent]

Hi ; thanks for your help. Things get better today after i repaired the primer pump. Misfiring started at 5000 rpm's. There was a vacuum leak on the pump. Tomorrow i'll replace it. I hope the problem will be resolved

Sorry for my English, i'm French:joyous:

Ps; by amelioration i meant improvement.

I'll give you news tomorrow

 

[99yam40]

I should have looked that up myself