Backfire at low revs

[donaldboyer]

Hi all,


1988 Merc 90hp
2 stroke, 3 cyl
Serial #0b312461


I have an issue with my engine in that it seems to back fire a little at low revs. I tried to video this today, but it wouldn't do it while I have the camera running! haha!

At low revs (900 - 1500 rpm) in OR out of the water, it occasionally backfires. Maybe 2 - 6 times a minute. Sometimes it's with a POP from the exhaust, and a puff of white/brownish smoke.

And sometimes it's just a puff of white smoke, revs drop 200-300.

The fuel is fresh. New switchbox and stator 12 months ago. Carbs cleaned and tuned about a years ago also.

I haven'y adjusted anything as I don't want to negatively affect things. So any advice would be appreciated.


Thanks,

Donald.

 

[Docksidemarineservices]

Your engine is experiencing a lean miss. Do as Kimcrwbr1 suggests, if this does not work, you will be removing the carbs for a good cleaning. You should start with a compression and leak down test before you do any thing. A leak down test will tell you exactly what condition your engine is in.

 

[racerone]

Open the low speed mixture screws 1/4 turn and see what happens.