1994 MERCURY KNOCK NOISE

[yap-yap]

SPARK PLUG BLEW OUT,REPAIRED THREAD,MOTOR NOW HAS KNOCK NOISE
COULD THE PISTON BE DAMAGED ?

 

[racerone]

A 2 HP or 250 HP ??

 

[yap-yap]

A 2 HP or 250 HP ??

1994 115 HP

 

[yap-yap]

NOT SURE IF SOME METAL SHAVINGS GOT IN DURING THREAD REPAIR.

 

[Chris1956]

Insert or helicoil was the correct length, say 3/8"? Spark plug is correct ?length as well.

 

[racerone]

Remove exhaust covers on side of engine.----Inspect pistons and rings.----How was this motor operated?-----What type of boat?----Oil injection in service?----Oil injection tested.----Oil injection pump still turning ?----Accurate compression test results should be posted.-----Overheat warning horn tested.----Impeller replaced every 5 years?

 

[yap-yap]

Thank you,I was sure I had a major problem until I noticed the top spark plug had no gap,it would appear that it was running on 3 cylinders causing rattle.

 

[racerone]

Sounds like a loose piston.----Hitting the sparkplug.----Good luck with this motor.

 

[ScottinAZ]

Sounds like a loose piston.----Hitting the sparkplug.----Good luck with this motor.

either that or too long a reach on the plug. if the plug is sitting too deep in the hole, its gonna hit something....