Spark Knock...

[Four86Winns]

After my Mercruiser 140 overheated (bad impeller) it developed a spark knock that goes away only when the timing is backed off to about 4 degrees ATDC.

Of course I know that the normal timing for this motor is 6 degrees.

Any ideas on how to solve this problem?

Thank you so much for your time, yall have helped a lot in the past.

 

[JustJason]

Re: Spark Knock...

keep the 6 and run higher octane.....

whats the compression at?

 

[Four86Winns]

Re: Spark Knock...

I haven't checked since before the problem; and compression was definitely where it should be. I know I have compression in all 4 cylinders, just not sure now much. I probably should get on that.