1992 Mercruiser 4.3L 262 CID Pre-Vortex Back Fires

[nic420]

1992 Bayliner 2252 w/ 1992 Mercrusier 4.3L keeps on backfiring. Just rebuilt the motor. Could be valve adjustment too tight or timing is off? Please assist w/ troubleshooting.

 

[nic420]

Backfires through the carb.

 

[Scott Danforth]

Timing off or you are running lean

 

[alldodge]

Could be valve adjustment too tight or timing is off?

Just rebuilt, I would think valves.
Assuming its a 1992

Valve lash is one additional turn after zero lash

 

[Scott Danforth]

zero lash is zero up/down movement when using your thumb and fore-finger

 

[Rick Stephens]

zero lash is zero up/down movement when using your thumb and fore-finger

Exactly. Not sure how many years I thought it was turning the push rod until you feel contact. You can get far too tight and never know it using that method.

 

[Lou C]

Even some of the manuals tell you to spin the pushrod, but the moving it up and down method I think is more accurate, I think friction can throw off the spinning the pushrod method.
If its backfiring through the carb an intake valve staying slightly open could cause that too, from too tight adjustment.

 

[nic420]

Even some of the manuals tell you to spin the pushrod, but the moving it up and down method I think is more accurate, I think friction can throw off the spinning the pushrod method.
If its backfiring through the carb an intake valve staying slightly open could cause that too, from too tight adjustment.

Thank you Lou! I was guessing it was the valves adjustment too because when I did them, all I did was bottom them out and backed out a little. I thought they were the torque type for the year of my boat (1992 Mercruiser 4.3L). Had a hard time starting so I backed out more until it was able to start. I thought that was it but now will take your's, Rick's, and Steve's advise. Gonna check timing and adjust the valves instead of just torquing them down to 20 lbs. Will let you know how it goes.