Logo
FULL SITE MENU

1995 115Mercury engine knock. Wrist pin or rod bearing

O

oran

New member
I bought this motor knowing it has a noise. I plan on rebuilding as I have good compression,and I will find out when I tear it down. My question is possible cause of this noise. It has a rattle noise at idle but not that loud. At 3/4 throttle the noise louder but when I come off plain it is the loudest. It is definatly isolated to one cyl. and the noise is a hard metallic rattle. I am thinking and hoping its a wrist pin bearing and not a rod bearing. What do you think. Also prior to me buying the motor one of the oil lines devolped a leak. Iwas told it was leaking but never broke off completly. thanks in advance.
 
Fairly common for the 2+2 motors.-----At idle it only runs on the top 2 carburetors and the bottom 2 cylinders barely get enuff oil to get proper lubrication.------My bet is the big end bearing !!
 
Thanks guys. Am I able to see inside the cyl. if I take off side plate? I am not running anyymore until I tear it down. Can you eliberate on the 2x2 alittle more and is there any updates for this low oiling effect?
 
If you take the exhaust cover off you will be able to see the pistons /rings and inspect for damage.-----------Have a 2000 - 115 HP on the repair stand now with major internal damage.
 
Can you eliberate on the 2x2 alittle more and is there any updates for this low oiling effect?
Click to expand...
Because the bottom two carbs do not have idle mixture screws they only allow fuel flow above 1750 RPM so the engine is basically running on the top two cylinders under 1800 RPM. My 2002 115 HP provides sufficient oil to the bottom two cylinders because it shows when checking the plugs...nice and wet oil residue.
 
Stop running it until you determine the cause! THose are expensive power heads to replace if it blows a rod.

Jeff
 
Back
Top